-HOME transfer to SV will be 1 way again, despite the full gen8 compatibility
So transfer from SwSh+PLA to SV is one-way, and any mon transferred to SV from Sword and Shield or Legends: Arceus cannot be transferred back.
I think this solidifies that "generations" as we see it are still a thing, and SV is very much a new generation of Pokemon by all hallmarks, being Gen 9, while PLA and SwSh are Gen 8. While GF doesn't technically number or name generations the same way we fans do, it's clear that SV is a new gen and a separate generation from PLA+SwSh, which despite the weirdness due to Dexit, the two games are still by all means technically the same gen as mons and be transferred to and fro SwSh and PLA and back between each other assuming the mon in question is in both games.
It's definitely in a similar vein to how Bank transfer between XY and ORAS, both being Gen 6, is two way between each other, but any mons transferred to SM or USUM (Gen 7) cannot be transferred back to a Gen 6 game, with the Alola games being a separate, newer generation from ORAS and XY.