My personal impression of events:
After leaving the Ruins of Silvermoon in Eversong Woods and defeating the Darnassian Scout, it's implied heavily that the Alliance was keeping tabs on them if not outright trying to sabotage their Arcane Sanctums and double-cross them on the premise of trying to look good, keeping up appearances, or lying through their teeth while doing so. It comes across as the Alliance being very petty and abusive, especially as at this point in BC questing it seemed like the Blood Elves hadn't completely put their lot in with the Horde and would only do so when they later ally with the Forsaken in Tranquillien, Ghostlands when the apothecary helps one of your out-runners - something you kind of eventually learn, is that Blood Elves were always just trying to get to Outland to reach Kael'thas before they realize his deception and betrayal. So, it really sinks in the feeling when you're in the Ghostlands that the Forsaken are the only real allies you have and the only other people who understand the pain the Blood Elves went through after the Scourge invasion.
(The Blood Elves have been hungry for all sorts of power ((and especially during BC, crystallized power, such like the Naaru ships that the Draenei arrive in and M'uru they drained power from was always the visual theme)), so events like them sending spies to Azuremyst always seemed pretty par for the course because of course gigantic crystal ships brimming with so much power it contaminated the wildlife there. Also, side-bar, the draenei were really quick to be able to artificially create immunity to the disease spread by the radiation of the crash and if the Draenei are this good at stopping disease they would've been really good advisors when it comes to the Gnomeregan fallout and even Plaguelands corruption, but that's not what the topic is about.)
Anyway, before you get to Shalandis Isle, it's a case up to this point of just one spy and Prospector Anvilward - one of which is hostile, outright trying to kill you on being discovered, but sure you may think that could just be his orders, kill anyone if you're discovered and get out of there, they're spies it's probably their job to maintain secrecy because them trying to spy and letting that get out would probably result in accusations that could lead to war (if not war against the Alliance, civil war of Blood Elves against maybe the Regent Lord or Farstriders who could have been said to allow spies this close to the capital which the quest straight up tells us about when dealing with Prospector Anvilward). With Prospector Anvilward, he also attacks and will try to kill the player upon being accused. But until this point these were just two people probably just following strict orders which were probably on some kind of pretense to prevent all-out war. But by the time you get to the Ghostlands, it's true that Prospector Anvilward wasn't killed in the open, but his sudden disappearance or lack of correspondence may have been discovered and perhaps more easily revealed or indicated with the Darnassian Scout's sudden disappearance or lack of correspondence and death which certainly wasn't hidden as well - you sure as heck don't go back to clean up the Night Elf corpse you just leave out in the middle of the woods. And especially considering there could have been scrying going on, maybe word reached that both the Darnassian Scout and Prospector Anvilward have been revealed and killed, which instead of capturing them may have been considered an act of war.
Even though it's presented to the player very clearly that the Blood Elves had good intentions and were defending themselves, the situation probably would not have been viewed this way by the Alliance. To the Alliance, two of your scouts and spies have been killed - one of which was there on the pretense of being an envoy, so while you may not know how the situation had unfolded, you do know at least that the Blood Elves aren't tolerating spies in their midst but at least your spies could get that close without being discovered and so far war hadn't broken out yet as a result of these two, so maybe they figure that a more removed or armed operation would succeed. As the Blood Elf player, whatever talks about the death of Prospector Anvilward and the Darnassian Scout are either non-existent or not made known to the player in any obvious fashion at this time so every encounter you've had with the Alliance so far has been them basically trying to spy on you, and then killing you when they're discovered, so it's no wonder then when they've put up camp on some island and have a couple outposts with scrying moon crystals all set up to spy on you even more - the Alliance clearly doesn't trust Blood Elves, probably a result of them wielding Arcane magic - which they didn't take kindly to at the time, and also they were draining M'uru in the basement of Silvermoon, which if the Alliance had been doing good spy work until this point, their recent sating of the hunger may have been something that would have been noted which may have been why the Darnassian Scout and Prospector Anvilward were even investigating the Arcane Sanctums in the first place.
The Alliance also having remnants of the key that was used by the traitor Dar'khan to take down the gate which was the only thing protecting your people from the Scourge also doesn't really bode well. The Alliance may have just been keeping the key in-case whatever new power the Blood Elves had ended up resulting in disaster that their people were used to with arcane trifling in the past such as with the Well of Eternity calling the Legion. And in truth, they would have had to have gotten the remnants of the key knowing of Dar'Khan's betrayal and possibly even his void research which also would have been taboo at the time (which eventually lead to the creation of the Void Elves). It may play a part in why the Alliance is so willing to work with the Void Elves, because of these situations with the Blood Elves they may now know with the M'uru's willingness to let itself be drained being revealed by Liadrin when she openly spoke to A'dal in Shattrath City - which was also foretold by Velen, that the Blood Elves would be redeemed and taken down a path to not join the Legion but fight against it as part of the Shattered Sun because of M'uru's noble sacrifice.