Yeah, it's not a clear-cut connection if you do it in multiple steps. Hence the caveat that there are ways to make it (more) true. But what improvement in anonymity does it provide over leaving them separate? If they can't infer that X belongs to you, then if you don't send it to account Y (linked to you) you certainly don't leak that X belongs to you. If you do, it's not proof, but it certainly doesn't improve matters.

Don't take it to extremes - this can clearly be stretched to include running the whole process through mixers and back to a single address while improving anonymity. It doesn't say that. In principle, is combining addresses better for anonymity than not?