A lot of stuff you learn as a beginner (keep hands up) are meant to be broken later on. For example, for hands up specifically, it's beneficial for an experienced person to drop it b/c it "baits" the opponent and keeps them guessing. IN boxing, we are learned to "close the door" and maintain a side stance, but as you get better you know you have to square up, b/c some punches require you to do so. dropping the hands is also good cuz there are jabs "from the hip" which are weaker but much faster and energetically efficient.
we also keep our hands up b/c we don't know how to defend yourself, so it's always good to keep defense on. as you get better, you know when to turn it on and off. im a short boxer, so i'm "supposed" to keep my ahdns up. my head movement got better, so sometimes drop my hands when fighting an inferior boxer b/c i know my head movement is good enough (parrying also partially blinds me, so i prefer head movement over parrying if that option is safe to use).
if u're not fedor or a good striker, just keep obeying the rules.
edit: also when i saw olympics, people in east europe (korea, or germany) tend to box in a stance similar to sub zero in MK, were both elbows are descended and forearms are horizontal to the floor.
