No, Sisvel and Avanci are.

How does that work? They force AOM to pay up and then I guess either AOM passes the royalty burden onto AV1 users or they take the hit and pay it themselves?

They did this, paid then off and took the hit, for some VP9 patents.

They also snipe away at the shittier parents in court.

Plus they have the "if you sue us over AV1 patents, you no longer get to use AV1 for free, patent landmines in place”.