It's definitely one of several possibilities. Keep in mind that Legion was supposedly being developed and planned around the same time as WoD. It's logical to assume, under those conditions, that much of the early content for Legion was built and designed under the same abortive "No-flying ever again" experiment that WoD was. It could be that Blizzard is building later content for Legion with flying in mind; hence the delay for obtaining it.
TRANSLATION: Keep flying locked so I can see other people annoyed by trash mobs. See: https://en.wikipedia.org/wiki/Schadenfreude
Sorry, that's not a valid reason to restrict flying. Also, you can't make a zone into a total joke when it's already a total joke.
And what's the problem with wanting to get to your enjoyment faster? Isn't that what instant teleports to dungeons or Battlegrounds does? Should we start forcing people to walk through zones without their mounts, just to reach instance entrances so they can PVP? Yes, WoW used to require that. No, it wasn't good then, either. Blizzard introduced teleporting to instances because it was convenient and good for the game and the players. Lets look at having to gather at the M+ entrance. How is the experience of the M+ run in ANY WAY improved by having to physically take the time to travel to the entrance? Explain that to me, please. It should be interesting.
As for "experiencing the game the way it's meant to be played"? IMHO the way Blizzard means for us to play is garbage. It's tedious. It's boring. A mazelike zone design filled with meaningless trash mobs does not make for a more engaging game. Maybe the first time through as I'm leveling it has some vague merit, but the second time? The fifth time? The hundredth time? Maybe some people like that experience? Fine! I don't try to impose my way of playing on them. They don't have to fly if they don't want to. More power to them. But as for me, give me the ability to choose what type of gameplay I want.
The entire "No-Flying" experiment is a joke.