dumb injection question

i know there's a gazillion online articles about dpfi to mpfi injector
upgrades for 88-91 civics, and most of these involve pm5 to pm6 ecu
swaps. but, looking at the schematics for both the dpfi [pm5] and mpfi
[pm6] ecu's, they both appear to be identical in pin-out's, with only
the injector and distributor wiring that's different. [typical honda
plug and play intercompatibility?]

so, if the basic functions and connections of the two ecu's are the
same, just with different injection maps, is there any reason why a pm6
ecu can't be run in dpfi mode?