Yes, that's a very good point. The keys I'm using are Cherry MX Clears which have an actuation force of 55cN. From my own experience, it would require a lot more force to depress a piano key. So yeah, maybe wrist flexion is pretty much required when playing piano to avoid muscular fatigue in the fingers.

>it would require a lot more force to depress a piano key

55cN is a little on the high side for force needed to depress a piano key ("touchweight"). But the piano is velocity sensitive, and pressing with the minimum force won't get you any sound. Playing loud notes takes substantially more force.