Yes, and... each of the earlier processors had certain 'corner cases' in the way they handled setting (or not) flag bits; DEC s/w had to check these corner case

Yes, and... each of the earlier processors had certain 'corner cases' in the way they handled setting (or not) flag bits; DEC s/w had to check these corner cases and execute a proper set of instructions for that specific machine. But yes, conceptually, the orthogonal addressing modes, and 'obvious' instruction names influenced probably 2 generations of students (for the better). The major lesson learned tho, I think, was: never be stingy with address bits! (16 is way too few; and even later 22-bit addresses weren't enough.)