Two things
First, looking at the BoardGameGeeks page for this, I noticed cards taking place in The Inner Sanctum (presumably of Silver Twilight Lodge). Now either thats for combining or FFG is using the same locations which is cool too.
My other guess is because the miniatures seem to have a AH monster chit sized slot in the bottom!
http://www.boardgamegeek.com/image/810696/mansions-of-madness
Maybe thats for something else, or maybe the just want to make them usable in Arkham aswell, but I think these are good guesses!
Thoughts?