Well, Ilia bumped McCoy off of the TMP movie poster. Saavik appeared with Kirk and Spock instead of McCoy on TWOK posters. McCoy is on TSFS poster, but Saavik is more prominent. All seven appear on TVH, together. It's just Kirk and Spock on TFF. The "Big Three," and only The Big Three, finally appear together on TUC poster.
Exactly. It's not like the previous generation of movie posters made a big deal of McCoy or "the Big Three."
This is nothing new.