Well, the offical Endwalker website confirmed

that the Magus Sisters are indeed going to be a trial, so I'm thinking my suspicion of the Tower of Zot versions just being cheap lunar knock-offs instead of the "real" deals in the full game is likely.

It just further makes me question when that trial would happen, though, since level ranges suggest Thavnair part 2 is seemingly right after Garlemald (Where we're likely already going to square off against Anima due to 83 being a very typical level for a trial), and I can't see the sisters fitting anywhere else in the story.

That would leave us without a trial boss for a very long time...unless it turns out we actually have more trials then the norm of three this time around.