The use of quotes is a nod to the mainstream norms that people have “leagues” and generally date within their league. Furthermore it’s a nod to the notion that fat women are not as valued by mainstream society and still experience a lot of discrimination and prejudice even as we’ve taken to accepting literally everything else around us. Hence their “league” is “lower” and if they’re dating someone perceived to be above it’s a mismatch.Lol, what does that even means, "mischatched couples" in that said context??
Again, use of quotes is significant because it’s not the way I personally feel so much as my observation of how our culture treats this.