I know, but it doesn't really make sense nor is it necessary for ET to be seeded. I don't get why they bothered to code that.
I found one weird thing. I've heard something about devil deals not being properly seeded so I did the same thing on one; first time I entered, it was three items. I left, died, killed the boss and from then on it was Krampus every time I tried (5 times again). Why would that happen? (I realize now that I should've probably tested it on more than one devil room...)
Basement XL floors are awesome. Free item rooms and a fast and easy devil room. Anything below that is terrible, though, since you miss one shop and one devil room per 2 floors.
Personally, I think the size between XL and normal is the best one. I think it happens (sometimes?) with Curse of the Lost, and sometimes it just happens for no particular reason.