Which I don't believe argues the point. You are relying on a gameplay system that for convenience tags them as Alliance to show their alignment to the Alliance and hostility towards the Horde when that isn't the argument. Their emotional position is accepted. The argument is that the Silver Covenant as an organisation, because of the Kirin Tor, is de facto neutral and cannot openly act against the Horde. If they were a true, active part of the Alliance, then why aren't they seen without Dalaran and where were they during the Fourth War?
Pandaria became the main conflict, but Gilenas, Ashenvale and Stonetalon fell at the start of the Cataclsym and Theramore was destroyed before Pandaria was found. The landmass was discovered as a consequence of a Horde attack upon an Alliance fleet, which drove them towards the continent. The war was already well underway at this point, the Pandaria conflict name refers to the most violent, destructive and decisive period of it.
As for thas'dorah, that was initiated by the Unseen Path. You were assisted by Veressa Windrunner. Veressa Windrunner is not shorthand for the Silver Covenant if the reason she is there is because it has to do with one of her sisters, as almost all her interactions have been recently. Her reason for being there in the thas'dorah questline were to see if she could find Alleria.
Your final point in this paragraph is the one I shall address first, as it seems to be the root of your misunderstanding here. The Speaker of the UK Parliament is elected from the sitting MPs. The sitting MPs were themselves elected in a first past the post electoral system on behalf of a political party. To even stand for election to the parliament, every member has therefore backed the position of their political party, argues for that position in debates and votes for that position once the debate concludes. Every single member therefore has a clearly expressed record of their thoughts and policy preferences. Yet the speakership only works if the person who holds the chair is perceived by all to be neutral. Those elected to the chair of the speaker must make the professional choice to set aside their partisan instincts and assume a neutral position. Using the current speaker as an example, everyone knows he is a Labour party member to his bones (left wing) yet he must set that aside to function as a neutral referee. Almost every person to hold the chair can be said to have successfully done the same.
The members of the Silver Covenant hate the Horde and wish to aid the Alliance. This is a fact. It is also a fact that in the recent, bloody war they did not do either. Either losses over the years have finally rendered them non-functional, or the neutrality of Dalaran (the city in which they now lived) compelled them to stay their hand, or a combination of both. It is more than possible to be partisan, yet circumstances enforce a de facto neutrality upon you. They may not aspire to neutrality as the speaker does, but neutrality is compelled upon them to safeguard Dalaran. After all, should a partisan militia begin attacking the Horde and then retreating to 'neutral' Dalaran after striking out, the Horde would rapidly conclude that Dalaran neutrality is a contradiction and render the city a target of attack.
This seems to be devolving into a debate over how exactly their situation is described. Individual exiles are partisan. Their organisation has had neutrality compelled upon it by the Kirin Tor.
The Silver Covenant uses the term Rangers rather than Farstriders. And what you are describing did not happen. Veressa never said a word, seemingly present only because of her connection to Sylvanas (her new role in the story is the windrunner family conflict). Instead, Lor'themar was taking with Shandris Feathermoon, with Lor'themar saying the Farstriders will hunt Sylvanas and Shandris Feathermoon saying the sentinels are also looking.
No High Elven force served the Alliance during the Fourth War. Individual High Elven exiles did, but to describe them as High Elven forces implies armies and attack squads of high elves. We have evidence for three high elven exiles who participated in the fourth war. Two of whom were shield mages who sat on the airship and didn't get their hands dirty. Frostfencer Seraphi is the only high elven exile to actively participate in the fourth war. The comment regarding the Silver Covenant being elsewhere is a little undercut given you confused the Silver Covenant rangers with Shandris Feathermoon's Night Elven sentinels.
Nor was the Silver Covenant mentioned in any of the mission table missions, the missions we have used to flesh out what did happen elsewhere during the war.
The three sisters comic shows Veressa, commander of the Silver Covenant, still dwells in the Greyfang Enclave.
Their profile in game has substantially diminished as well with the faction being barely used in Legion and not at all in BFA. Narratively, the Alliance now has a faction of thalassian elves of their very own. The Silver Covenant is rendered redundant as a foil for the Blood Elves as a result.
There is no evidence for this, and as three sisters proved, the Silver Covenant still seems to dwell in Greyfang Enclave. Assuming they all went elsewhere except for the leadership, when there is no evidence for that and such a move seems counter-intuitive for a militia, seems to be an attempt to dodge that the obvious conclusion is that there are less of them due to the numerous conflicts they have fought in but they still live in Dalaran.