Given the evidence Cushman presents, including:
- Nimoy having gotten a second Emmy nomination while Shatner was again passed over;
The Emmy nominations for 1966-67 were announced on May 1, 1967 (Cushman implies they were announced the week before June 1, 1967, but this is incorrect). These were the nominations for Star Trek's first season, not its second (to be fair, Cushman doesn't imply as much -- he only refers to Nimoy's first nomination).
What's crucial here is the fact that the revised (and final) story outline for "Wolf in the Fold" was already completed when the nominations were announced (it is dated April 21, 1967). As Indysolo has already noted, Spock's lack of a role was already an issue at this point. D.C. Fontana wrote to Gene Coon on April 25, 1967, and remarked, "Has it occurred to anyone that Mister Spock is hardly in this story either?"
In other words, this was always a story with a reduced role for Mister Spock. It was also, based on the memos from Justman, Coon, Fontana, and Roddenberry (which I've been lucky enough to be able to read in full), an episode that didn't start off with much of a role for the show's other two primary regulars, either. Kirk and McCoy had more to do by the time the episode went before the cameras; Spock didn't. One can read what they want into that, but there's absolutely no evidence that it was a direct move on Coon's part to minimize Nimoy's role to assuage Shatner's ego.
- Nimoy's salary battle at beginning of the second production season where Roddenberry went far enough to consider firing Nimoy
As far as I can tell, Cushman doesn't mention this. If he does, this doesn't make sense. Nimoy (successfully) held out for more money. The matter settled, the production wasn't about to intentionally feature less Spock (he was the show's breakout character). If for some reason the production did want to send Nimoy a message, giving him a reduced role in a single episode filmed midway through the second season's initial order hardly seems like a meaningful way to do it.
- The script for the episode filmed prior ("The Doomsday Machine") included large chunks of action where Shatner was not involved at all. In fact, Shatner felt compelled to cut Nimoy's lines (to the point Norman Spinrad stated that one scene no longer worked as written), suggesting Shatner thought Nimoy's prominence this the script could reinforce the notion that Nimoy was the "real" star of the show, not Shatner. Justman and Solow wrote extensively about that friction point in their book.
Notably, Cushman's only source about this re-writing of "The Doomsday Machine" is Norman Spinrad, decades after the fact. I haven't been able to compare the shooting script to the finished episode in enough detail to corroborate or disprove his memory, but judging by all the details Cushman gets wrong about the writing of this episode (chief among them his bizarre contention that Gene Coon came up with the idea to kill Decker, an idea that's actually in every outline and script for the episode), Cushman certainly didn't do this.
With these factors in mind, I find Cushman's analysis of the situation to be sound, logical, and supported by factual evidence from other sources (both Fontana's memo and the Solow/Justman book).
If you say so. Honestly, I don't follow his argument at all. Like much of the book, it's filled with speculation about people's motives that Cushman couldn't possibly know. In other words, fiction.
I'm certainly willing to entertain any contrary or different interpretations of why Spock is not a prominent character in the first half of this episode. However, until they are presented to me, with at least as much evidence that Cushman has presented, there's no "there there."
It seems much more likely to me that's Spock minor role was a problem that simply couldn't be fixed before the episode went before the cameras. Cushman suggests that Coon rushed the episode into production ahead of others to send a message to Shatner, but it seems much more likely that they simply had nothing else ready to film at this point (as was often the case).
While we're on this subject, let me say this: There are those--not necessarily you, Harvey--who have (at least implicitly) criticized others here for believing things simply because they appeared in Cushman's books. Those who would dismiss viewpoints, etc. simply because they come from a particular author without presenting factual, verifiable evidence that disproves the author's claims themselves display bias that discredits them... at least with me.
There are simply too many errors, large and small, for me to immediately believe anything Cushman asserts in these books without the backing of evidence. I'd be happy to talk in more detail about my issues with the books offline, but I have little interest in providing him fodder for a second (or, in the case of the first book, fourth!) edition of the book.