It says a lot. Just because it is a bias, doesn't make it wrong. I've meet enough people in my career that would prove the rule about attention to details.
Maybe I'm misunderstanding your point (or maybe this is your point), but doesn't this take effectively invalidate the entire human interviewing process? The whole thing is just a series of actions (portfolio review, phone screen, whatever) that give the reviwer(s) a set of mostly subjective data points from which they infer a candidate's fit for a particular role.
I've had plenty of recruiters that could ignore silly resume mistakes and find gem candidates. I've also hired candidates with horrible resumes, and it's never been a problem.
Evaluate a candidate based on their experience and qualifications, everything else is just to satisfy our own egos.
> Evaluate a candidate based on their experience and qualifications
Well, as I said I typically hire in design and product, so "proven ability to produce high-quality written content" is often an important qualification.
It says absolutely nothing. You've inferred something from it, and then run with it to create your own narrative.