In 1955 to 1958, there were more tower people and more dispatchers at Continental and other places to keep and eye on things and keep things moving.
I agree that it takes more people and cars to run at 34 tph than at 27 tph.
Today, many many jobs in the field have been cut in favor of putting more suits to push papers around downtown (you only had the TA building then, today you also have MTA headquarters and 130 Livingston).
I also agree that it takes even more people to explain why they can't run at 34 tph.
In those days, a train with 10 live cars had a higher top speed than a train to todays standards.
In those days they ran 11 live cars.
The higher top speed does not increase track capacity. (It actually decreases it). It does mean that it takes more equipment and personnel to operate and maintain it a given service level.