As somebody earlier pointed out, we’ve used hydrogen vehicles for about 150 years and there has been no explosions, Hindenburg aside.
From my research, you need an ignition source for their to be a risk or else it just combines with oxygen in the air almost instantaneously.
So you think an e-bike crash couldn’t possibly create a spark quick enough to ignite liquid hydrogen? Gee, I wonder what all those precautions we had to take when we refilled the hydrogen tanks on the warehouse equipment was for then?... And there were many.