Probably they want to know who is actually using Tor, instead of knowing what is being transported through it.
Just using it makes you automatically interesting to state actors.
I mean, UK's move against porn is even bolder, but I doubt it that Tor handles video well.
YouTube blocked the network request as suspicious though I was able to view the main page fine; I did not try creating a new circuit.
The Vimeo video played perfectly fine.
I kept creating new circuits until the exit node was US, and then the PBSKids video played fine.