Forbidden Sanctum Room Reveal Exploit

Discovered this unintentionally a few days ago.

I've only tried this on the first room on a floor, I don't know if it works halfway through one.

While you have the boon "Scrying Crystal: You can see an additional room ahead on the Sanctum Map"
1: Place a portal in the room with the bookstand where you select your next room.
2: Leave via the portal, which will take you to the Bridge Encampment in Act 7
3: Use the Waypoint to travel back to the Forbidden Sanctum
4: Enter through the chained door to resume your run. You should be back in the instance where you placed your portal to begin with.

Each time you repeat this, an additional room ahead is revealed on the map on the bookstand. By doing this 5-6 times, you can reveal the entire floor. Once you complete a room, this effect disappears and you will only see the regular number of rooms.

This doesn't seem to work with relics that reveal one additional room, just the boon.