Having nabbed the game I will confirm this. Though I will ALSO say the game itself isn't very good (as in the original Kinect Sports is legitimately better). Rule 63'ing yourself is about the only good part of the game.
Heck the game even advises it and gives an achievement for it! (The achievement is called "Curious" and you get it when you RE-make your avatar into the opposite of it's previous gender)
Having said that, the male characters are really disappointing as they do seem to feel the need to beef them up. They always seem to get a larger chin than you actually have and turn out more muscular. I personally turned into Groose somehow. And yeah saw this happen on another person;s video of them scanning themselves in so it's not just me.
In the off chance anyone is curious I just uploaded the third part of my Kinect Sports Rivals playthrough where I finally get my Rule 63 on. Provided you wanna see my ugly mug and listen to me ramble on XD It's probably a little uncomfortable to watch :P
https://www.youtube.com/watch?v=AyXN-VZEdJo
Alternately here's some pictures:
http://imgur.com/YCMIz4K
Also if you're wondering the "Child" option is useless. The visual difference is nearly nonexistant.