That appears to be true, yes. If there are any all-cloth MINIs on U.S. shores, there aren't very many.
I prefer the all-cloth sport seats, but I'm ending up with the all-leather sport seats (profile leather) instead. That's a very close second choice for me. I found another option, though: get the leatherette seats and add MINI cloth seat covers (the official ones that preserve the airbag capabilities). The leatherette is surprising just about everyone for its quality. (Some people even say the seat fit installation is better than the leather.) It's getting much harder to tell the difference between that and real leather. That way you can go naked

in spring and autumn and put on the covers in winter and summer.
Sport seats do seem to be fairly plentiful, but the leatherette is reasonably grippy. (The all-cloth seats really need the sport seats, I think. They seem pretty slick.) The U.K. accessories catalog has sport seats listed as a dealer-installed option, but the U.S. catalog that I saw doesn't yet. In theory, though, you should be able to fit sport seats later if you miss them.