And that's just about an ideal solution: neither throw in references that serve only as "continuity porn," without serving the story, nor make unnecessary contradictions of existing writings.
What the hell does "unnecessary contradictions" mean? That's a nonsensical concept when applied to Trek tie-ins. Pre-2000, when novels weren't expected to share a continuity, there were multiple different, incompatible ways of depicting the universe, the characters' backstories, and certain key events. I think my version of the end of Kirk's 5-year mission in
Ex Machina and
Forgotten History was the seventh overall, and there have been a couple more since then. There were two mutually incompatible versions of Kirk's
first mission as
Enterprise captain within a year of each other in comics and prose, and of course I offered a different one in
The Captain's Oath. There were as many different fates for "The Enterprise Incident"'s Romulan Commander as there were authors writing about her. Same for origins of the Mirror Universe -- depending on the book, it diverged in the Romulan War or in the Eugenics Wars or at the dawn of history. So it's impossible to define a single version of the older continuity that other books should be expected to follow.
Even today, the same still goes; the novels may have mostly agreed with each other up until recently, but the comics, games, and Titan "biographies" still strike their own independent paths. That's not "unnecessary," it's just the nature of the beast. Tie-in fiction is speculative, not authoritative. Like historical fiction, it imagines things that could've happened in the gaps between the events we know, but it makes no pretense that its conjectures are the "correct" answer. There's always more than one possibility that can be imagined and explored.
When I was reading Trek lit back in the '80s, part of the fun was seeing all the different, alternative ways that novelists reimagined the Trek universe and filtered it through their own creative visions and styles. It was the same pleasure I got from reading original science fiction and seeing the different ways authors imagined the future. The fact that they didn't fit with each other was a strength, not a weakness, because it let me experience a wider range of possibilities.
