WebKit already supports AVIF directly, but Safari disables that and relies on macOS’s image decoders, which currently don’t.[1] I imagine it’ll arrive at some point.
And apple doesn't give ios uses any choice. You are stuck dealing with those differences.
Yeah, that's by far the worst part. Imagine being stuck with IE indefinitely. :)
https://www.coywolf.news/webmaster/why-webkit-supports-avif-...