Wait until the AR glasses come out. I pretty much guarantee that media syncing will be a huge deal, and Apple had better get their iCloud act together by then.
iCloud is a shambles; and I say this as an Apple user for more than thirty years, and has pegged his career to Apple.
This is one of those things that will hopefully be opened up with more standardization. There's nobody to blame but ourselves for not enforcing this earlier, and hopefully in the future opening an MP3 file won't be harder than it was in 2005.
I have also had it do that thing, where my (non-DRMed) song, recorded from a CD, is replaced by the DRMed “radio edit” version of the song, from Apple Music.
That’s fun.
Whether or not the sync actually happens, or if the song stays on the original device, seems to be a crapshoot.
Safari bookmark syncing is … not good. It rearranges bookmarks, refuses to delete some, refuses to sync certain ones, according to some internal algorithm. Etc.