It literally is. They are saying that these people must not be competent because they are an ethnic background that isn't the majority. That is literally their entire argument. They throw out a stat related to % of diverse hires and then mentions that the country is majority white. It's possible the poster doesn't realise the implication of what they're claiming and I hope we can have a conductive discussion.
FYI - No sourcing on your prior stat. But regarding this topic, when assessing hiring discrimination based on race, you need to take account a combination of qualitative and quantitative data to make assertions about widespread mishiring. For example, in a sector like Aeronautic engineering, you would look at the demographics of graduated engineering students, demographics of the engineers that remain in the industry, qualitative data looking into why other demographics are not entering the field and that's just the beginning of the type of data that would need to be examined.
However, it seems that you've seen some high level stat online, and now, in your 'gut' feel like there must be discrimination against white people and the non-white people are unable to deliver good products. That's what is interpreted by 'diversity quotas' hurting products.