I don’t see how that could contradict a potential rematch in Kenobi. Just because Vader isn’t sure if Kenobi is alive doesn’t mean that they couldn’t have possibly faced since ROTS. Same thing with Tarkin.
Over all though, rigorous canonical consistency has never been a thing in Star Wars, no matter how much fans want it to be. The franchise’s canon is an ever-evolving thing, the only difference with the Disney reboot is that they actually acknowledged it.