With respect to on-time performance, an interval that doesn't operate is not part of the on-time performance statistics as they presently are computed.
AFAIK they used the same policy then. I don't like that policy either. OTOH, the only times during that period that I recall a train being taken out of service, or even being late, was due to a flash flood on Hillside Ave and the MBA strike in the mid 1950's. Service was dependable; they did not play games to inflate their OTP.
As to the other arguments, here we go again: do the words "no field shunting," "no automatic keyby," "timer," or "changes in work rules resulting from accidents (justifiably in railfans' eyes or otherwise)" mean anything whatsoever to Mr. Bauman? (and yes, I know the "prewar" IND equipment didn't have field shunting -- it was designed not to need field shunting)
The prewar IND equipment did have one piece of equipment lacking on the postwar fleet - brakes capable of stopping the train within 250 feet at the maximum attainable speed. This is the most relevant feature regarding both service capacity and safety.
I've read here about the Brooklyn Bridge Cable Railway's outstanding performance. The line had no automatic means of separating trains.
Distance between trains was automatically maintained to within a foot during the cable days. There were no recorded incidents of collisions on the bridge. All the collisions happened in the terminals, where the trains were no longer under the automatic separation provided by cable operation.
I'm not even sure it had signals.
Signals were not required during cable operation. Immediately after cable operation, they went to a signal system with 100 foot blocks. The signal system was wired to enforce a 700 foot back-to-front spacing between trains. This reduced service levels to 64 tph.