Unless what I read is incorrect (and it could be), it said that they aren't announcing the theme until the actual premiere (Sept 14th). Personally I find that if this is true, it is pretty absurd. How will they advertise the show leading up to it without giving away the theme?
Speaking as a marketing professional, there's actually been a big trend in the whole "mystery box" concept.
People seem to be willing to buy into paying for something without knowing 100% what they will get...as long as they trust the company of course.
Need proof? Look at Lego Collectable Minifigures, Funko's Mystery Minis, the plethora of Loot Crate variations out there, Collector's Corps, Smuggler's Bounty, I could go on and on.
Anyway, think of this as a really big mystery box. People are already salivating over any little kernel of information then can find about the new season.
Some might say that they're getting more buzz around people NOT knowing the theme than they would if they revealed it, and disappointed a chunk of their audience.
As for how that would work with a HHN maze...
Advertising that you're going to include some major set pieces from season 6 into the house will drive some AHS fans that might not have normally attended just to see what might be coming this season.
Then, the house might generate some interest from the attendees to see how the scenes they were part of get worked into the show and watch a few episodes.
It's what we call synergy (a big fancy buzzword).
Sorry. Not to turn this into the AHS marketing board. Just an opinion.