I guess that means my theory doesn't hold water. Oh, well. Maybe my memory is betraying me. Or perhaps I tuned all of that out because I didn't particularly like the standards.
I also remember the different-sized roll signs. Did you ever notice that none of them ever had Rockaway Parkway signs? Even though the Canarsie line was cut back in the 20s thereabouts, the roll signs still said "Canarsie". They must have figured that people would be smart enough to figure out where the train was headed without getting specific. Interestingly enough, those same signs did say "8th Ave.-Manhattan" even though the 8th Ave. station didn't open until 1931. It's much easier to distinguish 8th Ave. from 6th Ave. than Canarsie from Rockaway Parkway, apparently.
As I recall, the doors on the standards opened and closed smoothly and evenly, at about the same rate as the doors on the R-32s and R-38s today. Once in a while, one door would be improperly adjusted and would whip open and slam shut. If you tried holding it open, forget it. Those doors were wide enough so that an entire "Please keep hands OFF door" would fit on one door.
And I do remember the sickly paint scheme. Some cars were painted a dark green shade.