User blog comment:ChishioKunrin/I showed my dad RWBY/@comment-25555436-20150926133944/@comment-4010415-20150927034226

I think they decided to give him a little muscle tone on his chest simply because they decided Sora will be "more mature" in KH3. He definitely looks older than he was in KH2 and in the real world in Dream Drop Distance. Which... makes me wonder how much time has passed between Dream Drop Distance and KH3.

All I know is, fangirls like the V-neck shirt showing his chest.