This also ensures that it gets the most testing as early as possible.
On the other hand, for users who happen to be running Wayland, it may degrade their experience.
I’m using Sway, and in my experience it’s not uncommon that apps with no stable Wayland support (e.g. Rambox) spuriously no longer start under Wayland even though they used to.
As an avid Wayland user, I’d strongly prefer built-in but opt-in.