Funnily enough to add onto this, you could even argue they continue off 2009, which had 3 UCM houses:
The Wolfman - Meant to be Larry Talbot first inheriting the curse and seeing the carnage and horrors that come with it.
Dracula: Legacy in Blood - The house was all about The Calling, when all of Dracula's Brides, both old and new, would feed (as happening in the 2019 house), also giving fresh energy and power to the Brides, fresh enough for a certain other Bride to harvest later...
Frankenstein: Creation of the Damned - The house showed the creation of the Bride, and I believe actually ended the same way the 2019 house did with the Monster bringing the castle down (although I may be wrong on that, anyone with better knowledge please correct me if so).