You can check why it’s re-encoding, there’s some guides out there. In my case it was the subtitles! Turns out Safari can’t handle all types of subtitles. Might be worth looking into it.

Of course I have been down the rabbit hole. The software is wrong. Give me an option to bypass re-encoding, and instead of failing based on diagnostics like it does, just play the darn file the best you can. I only have so much patience and I prefer living with a samba share to play it in the exact same mpv player without problems rather than fighting software over something that is so simple and fundamental to a video player.