Strange, I was under the impression that GLW was the victim and removed from the series following some 'unpleasantness' caused by 'suits'. Considering it was the '60s, I have no reason to believe what she says isn't true.
That being said, I also found it gratifying to see various actors move in and out of some of the duty chairs. While it is accurate that there would only be one Captain, First Officer, Chief Medical Officer, and Chief Engineer, the remaining positions would have several candidates filling the chairs since the ship runs 24/7. Besides, it also made financial sense for the network to work things out that way.