It just basically combines your libraries now. So if the license is in use, nobody else can use it unless there are multiple licenses. Offline will still work for your own games and you can choose the best version to play. E.g. I have Isaac but only 1 dlc while my gf has all of the dlc so I can just play her version when she’s not playing it.
This is probably second or third time they mention it in patch notes despite it not being released on stable yet. Or at least I think it’s unreleased. Anyone on stable?