From Halopedia, the Halo wiki
It's possible that they'll fix the Waypoint article as they've done with several ones in the past (e.g. they got Kelly's birthdate wrong and changed it, plus a lot of smaller changes).
There are also several planets in Halo other than New Jerusalem that begin with "New": New Carthage, New Constantinople, New Harmony, and New Caracas (the full list is here).
There actually was a discussion about the new Waypoint info on Cygnus/New Jerusalem over here. Contact Harvest unambiguously states that New Jerusalem is a planet, and since the Waypoint articles have been wrong in the past and are more malleable than printed canon, we should probably assume the Contact Harvest version is still the canon one.
But yeah, Mount Haven was never confirmed to be on New Jerusalem.
