i agree, for the shower scene to not be immature - if it's meant to be an experiment on doing whatever one pleases with the character - then there should be pooping and other stuff, so that would create the "open character" experience (as in open world?)
but other than that, yeah, that scene is even silly

i'd say it's for knowing the safe position to place the camera, but that would be just an excuse, since i find the scene unnecessary to say the least

I think it's for the camera to know what to avoid, had the model no nipples, there could have been a "no-nipple" slip
but i find these nude shower scenes unnecessary anyway, not to say sexist