I believe on wobble tests a low score would correlate to a lower body fat percentage, which under conventional standards of Western beauty would be considered to be desirable.
In this case, however, the protagonists appear to be aiming to increase their wobble score, on the absurdly named "Wobble-ometer". This is a subversion of your expectations! Thence: humour.
It's quite highbrow though, I can see why it wouldn't land first thing on a Monday morning.