Actually, it's not what you think. We aren't over-zealous parents pushing our five-month-old son into sports (but it builds character! you can never have too much character!) when he can't even crawl. This is actually one of the cuter parts of EC (as if the BabyBjorn Little Potty thing wasn't cute enough, right? of course right).
What the BabyBeast is sporting is actually a two-piece EC-wear... I'm hesitant to call it an 'outfit,' because I'd never take him out wearing this. And 'infit?' (on an infant)
He has a prefold, folded to fit neatly between his chunky baby thighs, held up with what is usually called a prefold belt, but I call a 'stretchy headband I bought at WalMart on clearance.' (who said the MommaBeast wasn't smart?)
The point of this get-up (or 'infit') is that it is exceptionally easy to take off when it's time to potty the baby. Or, if you miss the cues and the baby potties on himself, it's incredibly easy to pop the soiled prefold off the baby and tuck a new one under the 'prefold belt/headband thing.'
Also, it maximizes the cute effect of chub.