Chrome doesn't use hardware acceleration for decoding any image codecs-- not for JPEG or WebP or AVIF. It has some code for it (using VA-API), but it's disabled by default. Hardware video decoders are generally hard to use for image decoding tasks.

Safari appears to be the only shipping browser using hardware decoding for JPEG and HEIF (HEVC based images). This is probably because vertical integration lets them make the decoders appropriate for image use.

Also, "AVIF video" is incorrect. AVIF is the image codec based on AV1 intra frames.

AVIF supports regular AV1 videos, there is no intra-only constraint. You can try this yourself with any AV1 video:

ffmpeg -i input.webm -c:v copy output.avif

You are right about Firefox and Chrome not using hardware decoding though, as such an AVIF video plays back poorly. And Chrome refuses to load an AVIF larger than 256 MB on my machine.