It’s plausible. There’s a detailed description of the computer operations of the rendezvous process here:
The process describes several different programs running on the CSM computer at different points; just activating a given program takes several keystrokes. Some of these programs are run as a backup in case there’s a problem with the LM computer; others are run to monitor the progress of the rendezvous.
To take one example:
To aid the CSM's tracking of the LM, the CMP runs program P76, LM Target Delta V. As input, the CMP gives P76 the key parameters of the LM's burn; the time of ignition and the expected velocity components in all three axis.
I think each one of those input values is around 5-6 keystrokes by itself.
As the process involves taking the CSM computer through at least P32, P76, P33, P35, P79, and selecting different data values to monitor, “hundreds of keystrokes” seems about right.