Sure they don't, but saying that you are going to force logically separate pages onto a single page is starting from a point of bad UX and trying to dig yourself out of it.
Sure, in practice many SPAs might be subpar, but then the debate shifts to "are SPAs are difficult to implement correctly," rather than "SPAs for blogging engines (necessarily) creates horrendous UX". There are existence proofs of well-designed SPAs with logically separate pages and excellent UX.
As an aside, someone who pattern matches on "SPA = horrendous UX" might not even notice a well-designed SPA, further entrenching their belief that SPAs are a Bad Idea from a UX perspective!