Those are somewhat separate concerns. You could have companies making independent hiring decisions while systematically discriminating against demographic groups, and you could also have companies all use the same system that systematically disadvantages certain individuals, but it's unrelated to their demographics and instead based on things like their resume not being easy to OCR.

In this case, the claim is that both are happening: companies aren't making decisions independently and they're doing so in a way that discriminates against certain demographics. But the evidence needed for each half of the claim is different.