It means an extra 9 rooms and 9 paraphernalia (items) altogether as the original floors were 3 X 3 rooms, opposed to the new 3 X 4 layout. But this gives more room for players to move around independently, as some characters will need to do, and allows for some interesting items back in the game that had to be dropped when the room count went down.
It also means a bigger box, which seems to come in at the same price as the smaller one, which is a bonus!
The only issue is that mats are double sided, and not being one to waste space the rear of the mat needs to be put to use. Maybe an alternative floor design with fewer rooms, or a different, simpler style game altogether, with all three mats joined to make a 'snakes and ladders' style game where protagonists progress through the house encountering all manner of evil spirits to try to make it to the end alive, or each mat belongs to one of three players, where game parts, including the spirit cards, are used to make a game where players are trying to summon the spirits De'Ath from the house.
Whatever happens the mat backs won't be blank!