Apart from the standard difficulties my students exhibit when I'm working with them on relative clauses in Latin (such as the idea that the relative pronoun has an entire existence within its own clause that is independent of its antecedent), I've noticed something similar with my upper level students in regard to abstract pronouns. We're reading Caesar this year in AP and he uses abstract pronouns "These things", "These men", etc... constantly and I have to stop and ensure that everyone is keeping up with all the "these" and "those" and "them" as we read. Frequently they want to treat these pronouns as true relatives; referring back to a specific word in a preceding clause. The notion that a single pronoun can refer collectively to an entire paragraph, or a single idea encapsulated in a phrase, can stop them at times. It's an interesting problem I'd not given much thought to before now.Right!
fyi: The relative pronouns are that, those, who, whom, whose, which, what, whatever, whoever, whomever, and whichever.
Composition textbooks tell you not to use a relative pronoun to refer to an entire paragraph or thought -- not unless you say "This paragraph" or "That thought" -- but writers do it all the time as far as I can tell. I certainly do.
I was gobsmacked when I learned, just two years ago, that using a naked "this" to refer to an entire idea was forbidden. After Katharine told me that a prohibition on using a naked "this" to refer to an idea or a paragraph was ridiculous, I decided to unforbid the practice and carry on as before.
Don't go by me, though. Until 2 years ago, I had never heard of relative pronouns.
Or relative clauses.