As I figure it, an "MC" machine is live tool capable with C axis control, but is NOT a "Y" axis machine.
A "Y" axis machine is fully live tool capable with C axis control, so I guess they drop the "MC" designation.
I used to run a NL2500Y and it was fully capable for doing any kind of pocket milling or offset holes either vertical or horizontal plane. The main limitation is it only had about 4" total Y axis travel (+-2") from 0 up to about 8" dia., after that the Y is limited by the compound angle of the X and Y interpolation.
You can still mill quite a bit using C X and Z if you program it that way, but having the Y axis really adds capability, and is also very useful for turning operations, eg. double stick holders or just tweaking offsets for centerlines on drills etc. I'm spoiled now, I can't imagine running a lathe without a Y axis.