Video seems to play at same speed regardless of song

[ChocoChopin]

I'm not sure whether I might be missing something, but as far as I can tell the video plays at the same speed in every instance. I can't find any actual webm videos of CatJam to test the custom BPM option. Same result with either of the available BPM calculation methods.

Edit: I just used a BPM tester to confirm. And funnily enough, it's 136-ish BPM, which is exactly the rate mentioned in the example custom default BPM.