This is highly annoying, especially for things like grenade and mortar kit in action camera mode as it means that any skill used interrupts the auto-attack functionality of holding LMB in action camera mode.
I tested this on a few things and it happens with pretty much any skill, try it by holding down any skill to get it to keep auto casting and then use any other skill and watch the skill you’re still holding the button down for no longer be casting.
This is highly frustrating and hopefully not the intended behavior of the new holding down any skill to auto cast it functionality as it seems very counter intuitive to the whole idea behind that.