I'm always puzzled by the assumption that just because continuity exists among different works, it makes each individual story incomprehensible on its own. I mean, every
story draws on elements from beyond its own limits -- on the characters' pasts and relationships, on the nature and history of the world they inhabit, etc. My go-to example is "The Cage" -- it's the very first Star Trek
story ever told, but the whole plot depends on what came before it, on the deadly mission to Rigel that the crew is recovering from and that's prompted Pike to re-examine his life. The viewer seeing it for the first time would have no prior knowledge of the Rigel mission or of the city of Mojave or of the slave trade on the Orion planets, yet that doesn't harm the story because what you need to know is right there in the story. Same with the second pilot -- we've never met Gary Mitchell before, nor have we met Kirk before at that point (if watching in production order), but a story whose drama is built around the pre-existing friendship between Kirk and Mitchell is still easy enough to understand. The references to their experiences at the Academy, Dimorus, etc. don't throw you out of the story or make you afraid you've missed something. Sure, in the case of the books, it's different because the option exists for actually seeing those earlier stories being referenced. But aside from that, it's not much different within the text itself. Just referencing something beyond a story doesn't make the story impossible to comprehend, because all
stories do that to some degree.