It's also apparently something that occasionally confuses module writers for WotC.
Spoiler: Spoilers for Tomb of Annihilation
In the Heart of Ubtao, Valindra Shadowmantle is said to have a teleportation circle she uses to get to and from Thay. She had no reason to come to the Heart before the Death Curse started, and as of any point the PCs are expected to potentially meet her there, it's been less than a month since the Death Curse began. There's no way she established a permanent Circle there in that time. It also talks about her "stepping into" the circle to go back to Thay, which, IIRC, is not how the spell works in this edition. (In 3e, the 9th level spell did work that way, though.)