Mostly, I'm not big enough to trigger anything there.

Also, since ISPs usually only get a single humongous IPv6 block, it's actually pretty hard to know what is okay to block. Somebody might be on a /48, /56 or /64 network but they might also just have a single IPv6 address. Since you're blocking quintillions of IP addresses with each /64 net, the risk of hitting innocent IPs is high.

Also also, I'm not sure if Google is actually prepared for such a case. Since all the requests coming from Invidious just seem like legit unauthenticated requests, it's hard to flag them on IPv6 when the IPs are fully randomized.

Still, Google is moving towards requiring a login for everything. So I assume that method won't work for much longer.