(This is not in CS because it is a factual question about anatomy and kinematics, rather than directly about the arts.)
Many electric bass players (please don’t call it a bass guitar) have a right-hand technique which involves bending the wrist at a right angle. Witness bassist extraordinaire Stanley Clarke, frinstance.
This position contracts the inside of the forearm, stretches the top of the forearm, and causes the tendons doing the work to bend at a right angle. (I can’t figure out why tendons don’t just pop out when you bend any joint at right angles, but I never took anatomy.)
It seems that this technique would cause incredible stress, vs. a position that keeps the wrist straight, such as in classical guitar, tennis, holding a knife, etc.
It does. This technique comes from trying to apply upright technique to the bass guitar. Also, some people think it looks cool. Most modern bassists (post Marcus Miller or thereabouts) tend not to do this. I went to a Marcus Miller workshop a couple of years ago and Marcus specifically said do not play with a bent wrist. He does and his wrist clicks rather unpleasantly when he rotates it.
Well, it’s just a personal preference, really. It’s very common and generally accepted to call them bass guitars, but the approach to the instrument is completely different than a guitar and much more akin to a bass (double bass, contrabass, upright bass, string bass, bass viol, bass fiddle, whatever you’d like to call that). I’m definitely in a very small minority.