The answer to your question is that it is a game system. There is no reason for flight to be locked in the first place. You have flying mounts and they should not forget how to fly until some arbitrary requirements are met. But if we're going to have those requirements, they don't need to be stretched long enough for all zones to be available in an expansion. Pathfinder part 1 could unlock flying for the starting zones, then add forced safe landing as you approach a new zone until you unlock flying there via pathfinder part 2. (That's just an example using pathfinder like in Legion and BfA with the two-part system, though I think the system should still be changed.)
If flying in open world content is like gearing in raids, does that mean that gears don't matter in open world content? I don't think that's the case. The thing that you say gearing does to raids is the same thing that it does in open world content.When you can do said content even at minimum ilvl, gear beyond that point, just like speed and the ability to avoid dangers beyond what is necessary to reach all necessary parts of a map, is mere facilitator/accelerator. Does the ability to nullify dangers, including barely-avoidable rares and the like who could one-shot you vs. being one-shot by avoidable raid mechanics, matter for one but not the other? That seems inconsistent.
I have to disagree; the closest parallel clearly seems to be overgearing / gearing beyond what is absolutely necessary, as would nullify certain dangers and make the process on the whole quicker.
So flying does not replace gears. Again, flying is transportation. It is the difference between someone being summoned/teleported to a raid or going there manually. That is the closest parallel.
The content that you do in the open world still requires you to be grounded. That's where your gears will help you, not flying.
I'm not sure what you even mean with the parts in bold, haha.Depends. Is your point that "the world PvP environment caused my mounts, typically considered worse for world PvP's enjoyability, is an added risk that WoW players chose when playing on a PvP server (formerly) or on Warmode (now), knowing that flight would eventually be unlocked anyways"?
Anyways, flying/mounting itself is not so much a risk, but a feature of the open world setting. If people want a more controlled environment, that's what instanced pvp is for, and that's also where you get two willing parties ready to fight each other.