You’ve had good luck, then. If the group you’re joining happens, out of sheer luck, to be on the same shard as you, then there’s no need to go to a sanctuary zone to join.
However, I see nothing in the 9.1 notes about a change, and from recent reports I see, joining a group from a sanctuary zone is still required.
I’m only after what’s true and correct so if you have some link or patch notes or anything about a change, I’d be happy to read it and stand corrected.
The 9.1 patch notes say nothing, and when I search for “Maw phasing change” I only get information about the change Blizz made (around the end of November 2020) reverting the need to do this “sanctuary-zone-group-joining” in the entirety of Shadowlands zones. At that point, they rescinded the requirement on every zone except max-level Maw.
And here is a current support article, also stating the same need to be in a sanctuary area, and subsequently enter the Maw, to see your chosen group:
Since many gripe about this Maw-group requirement, I’d assume that a change to remove the requirements would result in at least a happy forum thread or a Wowhead or Icy Veins article. I see nothing of the sort, though.