The promotion may have simply been Majel pulling some behind the scene strings. When it was originally planned as the Phase II television project, even though the Spock replacement of Lt. Xon (David Gautreaux) was pretty much firmed up, he was suddenly asked to come in for a second screen test. Majel was apparently worried the younger Xon meant her character's primary obsession with Spock would result in her having a smaller role in the new series.
Suddenly some British actor (does anyone know the name?) had been brought in to test, and he was about Majel's age (mid-to-late 40s). But the guy did a poor audition, and Gautreaux was buoyed with confidence for a while. Gautreaux tells the story in Shatner's Star Trek Movie Memories