The PS Vita browser is an oldish Webkit build with JS 1.7, half-implemented HTML5, and a handful of features disabled. Its user agent is something like "Mozilla/5.0 (Playstation Vita 1.50) AppleWebKit/531.22.8 (KHTML, like Gecko) Silk/3.2", and it probably advertises a feature set close to Chrome builds from about a year ago.

I'm not too surprised that it doesn't support this gimmicky site, nor that it slipped through the feature/agent sniffing.