Which doesn't come across in a condescending manner at all and dismissive of the reader experience.
Whaaaaaaa...???? On the contrary, it's all about being considerate of the reader experience, keeping in mind that you need to make a story accessible to all readers. Is it condescending for a carpenter to say they know how to install a door? No. It's a factual statement that they have learned the basic skills of their profession and are thus qualified to make a structure accessible to its users. Exposition is writing 101, one of the most elementary tools in the author's kit. "Never assume your audience knows something, make sure you explain it in the text" is something that was drilled into me in grade school English class. (Which confused me greatly at the time, because the only person who read my papers was the teacher, who
did already know it. In retrospect, I see that it was training for writing for a larger audience in the future.)
You seem to be talking about whether a book is connected to some bit of onscreen continuity or tells an unrelated story, and my point is that
that doesn't matter when it comes to how exposition works. "Never assume your audience knows something." Any story, even a sequel, may be a reader's first, so you have to write it to work entirely on its own, to be understandable and satisfying even to a reader who's never encountered its characters and continuity before. A reader who knows the backstory being referenced may get more out of it due to the resonances, but that's not "homework," because it's optional. Every story should work on its own; connections to other stories should be a bonus.
Some people might seek out a book about Rios getting his ship or Seven joining the Rangers because they're curious about those untold parts of the continuity -- but those stories are only worth telling if there's actually a good story there that deserves to be told and would be enjoyable even to a continuity novice. Which I guess might be what you're saying -- that the continuity ties shouldn't overwhelm the story, that they should only be discussed in the text to the extent that they're relevant to its own narrative, so that they feel like part of the story itself rather than a hyperlink to something else.