In general doing a sub-I is a good idea, but programs never have this as an expectation. At best you can only do a couple of places and with people applying to 30 places... well the math should be obvious. In general, I think most programs do interview sub-Is. It is just easier to interview them as opposed to interviewing some but not all and have everyone talking about it. On the applicant side, you might as well go for it. Even if it goes the other way and the program doesn't like you, you wouldn't want to be there anyway. It is best that both sides figure this out before rank lists go in.