More a matter of taste than acoustics IMO. More people like the large chamber sound on tenor, more like the small and medium chamber sound on alto. Sure, pitching a small chamber is different and maybe sub-optimal, but not insurmountably so.I remember reading somewhere that a small chamber doesn't work on tenor for reasons of acoustics.
A medium chamber (same size as the bore) is as small as they can go otherwise it messes things up.
A mouthpiece expert can probably explain why this is.
As far as current rollover small chambers, Selmer Soloist, Meyer should still do a small chamber if you can find one, Jody's HR* is a medium-small chamber.