But if you're not gonna ship it to all your millions of users and receive the outrage as feedback, how will you ever know if it works or not?
A/B testing to a few users only works in web-app front-ends, not in professional tools where all single end-user releases need to look and act exactly the same.
Shipping to only a handful of users wasn't a thing in the era of "Gold CD" releases, and even in the era of the internet updates, nobody will want to take part in A/B testing and end up with a different Photoshop UX than what his colleague is using, so you either ship to all or none.
So it seems Photoshop's UI is more of a cause of inertia and resistance to change, rather than nailing right the first time.