As I recall in R12, it was the AME (Advanced Modeling Extension) that worked with "solids" after a type (non-Acis). AME was an aftermarket add-on, that was not fully under the control of ADESK, though marketed by them as an extension to autocad.
R13 was the first with ACIS solids, and the order there was always as it is now.... and that was over 10 years ago.
BTW, strictly speaking, -4+6=2 is addition not subtraction, you're adding 6 to the starting number.