To some extent, sure. But, in regards to the Star Trek franchise, I've heard (but willing to be shown otherwise) that there was a policy that only the TV episodes and movies are official. Events in the novels didn't occur in the TV universe.
That's not a policy, that's the default for how it routinely works. Novels and comics have almost
never been counted as part of the original work's universe. As a matter of course, the original work is its own thing, and the tie-ins are extrapolations made by other people, so they're a step removed from what the original creators did/are doing and thus there's no reason to expect the original creators to be bound by them. The term originated to describe Arthur Conan Doyle's Sherlock Holmes stories in order to discuss them in comparison to the stage play and various pastiches of the sort we'd now call fan fiction.
In 1989, Gene Roddenberry and his assistant Richard Arnold did issue a letter which
clarified to the public that the tie-ins didn't count, but that just because some fans were assuming the tie-ins
did count and that offended Roddenberry's ego, since he'd gotten very possessive of Trek by that point and liked to insist that only the Trek productions he personally oversaw were legitimate. But that was just his own personal hang-up. Fans have assumed it was some official doctrine from the studio, but it was just one insecure old man and his overbearing assistant feeling a need to mark their territory and say "No, Gene invented the Romulans, not Diane Duane" (even though it was actually Paul Schneider who invented the Romulans). The whole reason it left such an impression on fandom was that it was
rare. And that's because it's rarely actually been necessary or useful. That one damn letter did so much to warp fandom's idea of what canon is and spawn decades of ignorant, pointless arguments over non-issues.
However, there were some efforts made to make the TV episodes consistent with the TV universe.
That is completely obvious. As a rule, yes, fictional universes do make some effort to create an illusion of consistency. But where the canon fanatics get it wrong is in their expectation that a canon must be
absolutely consistent, which is virtually never the case. Even series with strong continuity inevitably contain mistakes and retcons, and some have much looser continuity. And that has
absolutely nothing to do with the word "canon." Canon does not mean continuity. "The canon" is a term of criticism for the overall original work. It is not a label that gets applied to each detail individually. The canon is the overall whole that pretends to represent a consistent reality, but which will almost certainly have some degree of inconsistency on the fine scale.
I'm sure from your perspective you don't use it much because you're on the non-canon side of content so it's really a non-issue for you.
For your information, I was writing original science fiction years before I sold my first
Star Trek story. At present, roughly half my published works are original (though all but one are short fiction, so my published tie-in word count is higher). So yes, in fact, I am speaking from the perspective of the creator of a fictional universe. I have two ongoing SF universes of my own. And I have treated both those "canons" as mutable and subject to change -- because that's how creativity happens in the first place, by trial and error and revision and refinement. My view of my main original universe has transformed enormously over the decades that I've been developing it, and I now consider elements of my first published story to be apocryphal. As for my other universe, the "Hub" series of comedy stories in
Analog, the first two stories were published with mistakes -- entirely my own fault in the second case -- so when I collected them in one volume, I revised them with the corrections made and took the opportunity to expand them as well.
When I was starting out, I was very annoyed by inconsistencies in fiction and made a pledge to myself to avoid them in my own work, to make sure that everything was as completely consistent and free of contradiction as possible. But over the years, even though I've mostly tried to stay true to that, I've still made mistakes that needed to be corrected, I've made scientific assumptions that were supplanted by later research, and I've learned from experience and realized that some of my early approaches to characterization needed rethinking. Every creative work is the result of a process, and any ongoing creation will continue to evolve and grow.
However, there is a practical side to having an official canon where there is a common set of "official" content.
The point is,
that is a given. It is not something that needs to be formally defined. That's the myth that's grown in fandom based on anomalies like the Roddenberry letter. It's a matter of course that the work from the actual owner of the property is the core work and that the work from publishers under license from the owner are secondary. That's obvious, but fandom has absurdly overcomplicated the question because of these silly misunderstandings of a very simple concept. It's like arguing over whether water is wet. The fact that something is land rather than water is not something that needs to be formally declared by some official or debated over by nautical fandom or whatever. It's just what the things
already are.
