I don't know?
William Windom said it was the most unhappy set he ever worked on.
You know, its strange. In the summer of 1991 I was at a Trek convention up here in Toronto and Walter Koenig was being asked various questions by the audience, many of which pertained to the yet-to-be-released ST6 and a few regarding his experience working on ST5 under direction of Shatner. I distinctly remember Koenig carefully responding to a question on whether he was able to throw a few ideas into the mix on ST5 and it was along the lines of "you don't want to step in on Bill's agenda....to have to deal with the fallout and an ego like that"
Koenig seemed very balanced and reasonable at all points. He didn't ping with me as some sort of overbearing ego. So I really don't know.
Is it possible that Blackburn was angled (and perhaps more behind the curtain) as damage control? Yet on the other hand it did seem like they were all having a good time all those decades ago....and the home movies took place over 3 years.....not during a happy afternoon one week early on.
BTW - I'm assuming that's the dog Shatner had the studio buy breakfast for each morning. Lol!