Access to hardware acceleration has absolutely nothing to do with the standards of the formats themselves. Clearly, since open implementations exist, open source developers know how the formats function. The problem with HW accel is that hardware vendors keep the details of how to access functions of the hardware is kept secret or otherwise locked behind proprietary code. But the same can be true of completely open standards like AV1.
> since open implementations exist, open source developers know how the formats function.
These formats are way more complicated than you think they are. Just because open source implementations decode/encode something doesn't mean the implementation is standard-compliant. My one certainly is not.
