>>39641269>>39641337>>39641337>>39641416THE POINT IS THEY DON'T
Literally the thing in the OP is the EXCEPTION here. Every fucking other thing the PC does either slightly or drastically changes their facial expression. The shot in the OP has the PC just doing their idle pose watching the events. That doesn't mean they ONLY do their idle pose in cutscenes because we've seen PLENTY of times where they are doing different things.
In SM, the protag had that stupid blank expression the whole time cause they didn't bother to make new face textures for them. They actually emoted during Z-moves because that was using a different model with a mouth rig and texture eyes. In S/S, now all NPCs and the PC have full facerigs ALL THE TIME and they're clearly way more expressive.