I know the adhesive will fail. I haven't had any issues with the premium but I've used it sparingly. I do just enough tile that having thinset let over isn't the end of the world. But I've had a few places where I've needed a bit of the premium. You would want to make sure that it gets a chance to dry and cure before regrouting. The premium does have an advantage over adhesives that are water soluble.

I think it does depend on the substrate. And how quickly things can dry. That's one of the things that is interesting between Schlueter and Pro-va membranes. Modified vs unmodified thinsets.