Yeah, I think it's because next to everyone else in SSB, Marth is pretty...normal. Take away his context, and he's kind of...well, boring. So I guess they have to spice it up so he doesn't get lost in the background.

She has a talent for writing and drawing, but I wish she didn't do all those terrible things to Marth D: But yeah, she did write Marth as an adult male ruler, which was, uh, rare.