Thank you, everyone, for all of the responses. After the discussion, I can at least rephrase my terminology from "reversed" to "opposite" in the panning. Then hopefully neither the Roland MT-32 familiy and the later GM families won't be upset.
So I think Falcosoft gave me the primary answer I was looking for -- that is, whether the MT-32, CM32-L, and LAPC-I all shared the same panning assignments -- which he said that they do.
However, was there ever an instance of mislabeling the R/L output stereo jacks? Someone thought that the LAPC-1 might have had mislabelled jacks.