The terms, mini, micro and baby seem to have originated with Seig. I don't know that there is really much use to more fine grained than "small bench top" lathe' at most maybe "Table top" to distinguish the smaller easily moved (under 100lbs) from the larger more static models.
Swing obviously plays some part in this' but an Atlas /Craftsman 6x18" with its greater weight, and rear mounted motor is much less portable than a 7x14.
