^No, it has nothing to do with that. We already knew from TMP that there was a gap of two and a half years between the time Kirk was promoted to admiral and the time TMP occurred. What fandom disagreed upon was whether there was a second 5-year mission between
TOS and Kirk's promotion. As I said, in the '80s the chronology of the 23rd century was vaguely enough defined that there was confusion about how much time passed between TOS and TMP. The prevailing view, supported by TMP's own dialogue, was always that there was a single 5-year mission, then 2.5 years of Kirk as an admiral, then TMP, then a second mission that was generally assumed to be 5 years. But there was a minority view that there were two 5-year missions before Kirk's promotion, and that view is at least implicitly reflected in several of the '80s novels, notably Diane Duane's books and Pawns and Symbols
. Note that none of them ever actually came out and said "This is a second 5-year mission," but they had specific references to the stories taking place several years after TOS episodes (in particular, The Romulan Way
was said to be 8 years after "The Enterprise Incident") even though the characters still had their TOS-era ranks, uniforms, and jobs. Thus we can extrapolate that the writers were assuming a second 5-year mission -- or at least were assuming that the in-story interval between TOS and TMP matched the real-world interval, rather than being years shorter as we now accept it to be.