I mean, I know nothing about what it truly takes to construct a HHN maze, but May doesn't seem that late, plus the team already has a preexisting relationship with Jordan. We have heard that the pitch went extremely well.
This quote from Murdy in the press release is also interesting: "It’s an honor to have the opportunity to work with [Jordan] and his talented team to bring his unique vision for Us to life as a ‘living horror movie’ as part of ‘Halloween Horror Nights." Sounds like it's going to be very collaborative, and having more hands on deck could help with a truncated design/creation process.
Again, the only thing holding this maze back is the shorter timeframe. I find it hard to believe that Universal won't go whole hog on this one.