Hiring is, as a whole, biased for the wealthy etc. Being privileged gives you a leg up on everything, from quality of education, to coping skills, to general health, so you would totally expect all parts of hiring to be biased massively towards privileged people.

I don't think a resume's level of polish is more biased towards social status than any other part of the process, and as such I think it's just as reasonable as anything else to filter on.

Anyway, resume quality is arguably just as relevant to a software job as being able to whiteboard code, if not moreso. Structuring design documents in a way that wealthy people like them (i.e. the old white dudes who run the company) is one of the most relevant job skills you can have to be honest.