Previous codes have been designed and sold as patented codecs. AV1 is meant to be royalty free by design. The claimants of the alleged patents can ask for money, but eventually somebody will refuse due to the very explicit royalty-free promise in AV1, and there should be a lawsuit. We have not seen that yet. As a practical matter, even if people are paying money silently, it would get on the grapevine. We haven't even seen any evidence of that either.

Even if creator said it's royalty free!, it's not guaranteed that there are no patent violation.

Hence, we would hear if people are being 1) sued, or 2) or are paying. We haven't seen any evidence of either.

A submarine patent approach implies waiting for it to become popular enough that you can extort companies into paying, rather than just dropping the codec in lieu of something else.