a writer decades later who can't resist throwing in a bunch of references to historical events and people that the original author wouldn't have considered relevant or appropriate to include

I think you've put your finger on something that often subconsciously jars about novels set in the past; they tend to emphasise the elements that the readership is likely to associate with that era rather than the ones that might have seemed more important to the characters. So the background events that the author chooses to emphasise are often ones that people of that era might have taken entirely for granted -- the classic example being that Jane Austen famously doesn't mention Napoleon in any of her books :-D