Besides the fretting hand benefits, this'll do wonders for your plucking hand. A straight and low wrist is key to doing CTS-free 200bpm 16ths with only 2 fingers.
On the fretting hand, some folks new to the posture confuse lateral deltoid and upper arm fatigue with wrist/hand pain. The former is natural & safe as your lateral deltoid is getting a real workout to keep that arm up and engaged. It becomes a non-issue after a couple weeks. Similar issue with spinal erectors causing lower back fatigue early on to carry the instrument's weight, esp because you can't easily kick back in your chair and play in weird and unhealthy positions. It'll go away with regular practice (...or deadlifts).