hmm....this could be an idea. as you said: ms want unified experience. so why not give it full.
Maybe it should. If Microsoft wants one experience and a shared UI. They wouldn't really be breaking anything. But legacy users might get confused
generally, you're right, legacy users could be confused on such "first-use & everyday-use" modifications. but then, we are talking here about a change to one single swipe for a feature so easy to learn that is still easy to relearn(after all, app list is used everyday so you can re-learn quick how it works). plus wp have that arrow at the button which reminds us everytime where we need to swipe.