I agree with your post fully.
Roblox’s ultimate vision of cross-play everywhere can not interfere with developer’s wishes to be on all platforms, but to create a game with equal opportunity gameplay -stemming from the same controls per server. (2 bulletpoint in the OP)
An example in the past was a time when the developer could not turn off their game from mobile players, hence getting bad ratings from an unoptimized mobile experience that many developers did not want to deal with at the time. This would be an example of Roblox’s vision of cross platform ruining developers’ experience with doing what they want. It turned out to be a big win for both parties once it was the developer’s choice of when to be ready for mobile players in their game.