It's not about that, it's about the phrasing "swim in your lane". That means imposing social rules, and belittling people who behave differently. Taken in extremis, it can be interpreted as: ugly should only date ugly.
No, you're misinterpreting it, maybe even projecting your own insecurities. Nobody said you have to date fit / thin people - just that people shouldn't lie / pretend about it. You have a fetish on fatties? Set the weight filter up high. This is clearly superior to the current model, where it's easy for people to lie about weight/age/height/income/...
The real criticism of this model is completely different, and much deeper. People don't actually know what they want and who would make them happy, and they often conform / default to social conventions in their public preferences - e.g. maybe you want to filter out 10+ older men because you don't want to go on dates with "creepy" dudes, or you want to filter out fat women because you don't want your friends to judge you - even though in reality, you might actually be happier with those matches, or, more likely, those attributes are often orthogonal to your actual happiness.
The real criticism of this model is completely different, and much deeper. People don't actually know what they want and who would make them happy, and they often conform / default to social conventions in their public preferences - e.g. maybe you want to filter out 10+ older men because you don't want to go on dates with "creepy" dudes, or you want to filter out fat women because you don't want your friends to judge you - even though in reality, you might actually be happier with those matches, or, more likely, those attributes are often orthogonal to your actual happiness.