Well, Corona had a few problems with details like that. For instance, it mentioned that Spock was in his 80s -- which, in isolation, was a reasonable extrapolation from the fact that Vulcans are supposed to have a life expectancy of 200-plus, but it overlooked the fact that Amanda looked no older than her 60s when we saw her in "Journey to Babel." Which was presumably the result of the conflict between the writers' need to draw on the incarnation of Trek they knew the best (TOS) and the cover designers' and marketers' desire to tie in with the imagery of the recent or current movies. Of the early Pocket novels (first 35-ish) that had movie-era cover imagery, the only ones that actually took place in the movie era (not counting actual movie novelizations) were The Covenant of the Crown, The Prometheus Design, Triangle (which has movie-era Kirk and Spock and TV-era Enterprise), Dwellers in the Crucible (no ships or uniforms visible, but Kirk and Spock look older), and Deep Domain. The later novels Ice Trap and The Better Man have the reverse problem -- they're set in the movie era but have TV-era cover imagery.