Interesting about the broken Peertube federation. I'm following a few channels (mostly for testing purposes) and I did get new posts to them from PT's side and saw my votes reflected on each end. Haven't gone back and done any comparison's lately, though. That post says it hasn't worked in ~3 months. If it's a Lemmy issue, It's possible that it works for me since my instance is still on 0.18.5? If something changed with Peertube, then I may have just not noticed. Will check on that when I have some time as I'm now curious.
Update: Seems the ones I got were just from the initial fetch.
Update #2: A new PT video came through this morning on one of the channels I follow. So maybe federation does work but is just wonky/inconsistent? Again, I'm still on 0.18.5 so may have something to do with it.
Regardless, yeah, like you said, they'll still embed when brought over manually.