June 1954 was before December 1, 1955, when the Queens Boulevard Line started feeding the 60th Street Tunnel; at the time, only the Astoria Line fed the tunnel.
Are you suggesting that Astoria service was reduced, when BMT service to Forest Hills was started?
The current scheduled departures shows some interesting conflicts. Assuming that the travel time from Queens Plaza via the 11th St Connector is roughly the same time as it takes trains from Queensboro Plaza to reach the merge point. Look at the scheduled departures:
N leaving Queensboro Plaza: 8:00, 8:10, 8:20, 8:29-1/2, 8:37-1/2, 8:45-1/2, hold to 8:57-1/2 = 7 trains
W leaving Queensboro Plaza: 8:05, 8:15, 8:25, 8:33, 8:44, hold to 8:50, 8:55-1/2 = 7 trains
R leaving Queens Plaza: 8:03, 8:09, 8:15, 8:21, 8:27, 8:33, 8:39, 8:45, 8:52 = 9 trains
Total = 23 trains (and no, that's not full utilization)
There's a conflict between the R leaving Queens Plaza at 8:15, with the W leaving Queensboro Plaza at the same time. There is a similar conflict for 8:33 departures for the same two routes.
In addition, assume that it takes about 1 minute for a train to clear that interlocking. The R leaving at 8:09 will conflict with the N that leaves at 8:10; the R leaving at 8:21 will conflict with the N that left at 8:20 and the R leaving at 8:45 will conflict with the N that will leave at 8:45½.
So, of the 9 R trains during that period, 5 were scheduled to leave at times that would conflict with Astoria service.