In my last Infinite Archives run I got the Beastial Transformation (many times).
I decided to switch Champion Points before facing Tho'at (after entering her arena, before starting fight), but upon confirming the CP changes all active skills disappeared from the bar, and I was unable to light- or heavy attack.
Adjusting CP while transformed apparently reduces you to a state where you can only Block, Bash, and Roll-Dodge.
I haven't tested it, but I would assume the same thing applies to the transformation in Stone Garden, although it's less of an issue there, being time-limited.
I think it is central to ESO's well-being to critique the developers when they change the game (or fail to change something).
But the negativity can be exhausting, so I vow to post 50/50 negativity and appreciation.