Safari not playing VP9 codec videos in MP4 containers

Pretty straighforward, even after iOS added full upport for the VP9 codec a while ago, Safari still had issues when the VP9 video stream was inside an .mp4 container file, instead of a .webm, and wouldn't play back those videos.

When I did some testing in the iOS 18 beta earlier this year, it seemed like the issue had finally been fixed and Safari would play videos of that type, but now in the release version of iOS 18 it seems to be broken again.