That bit made no sense to me.

I think the opposite is true; when given no concrete feedback, one begins to hypothesize why they were rejected, and their mind will often point them to discrimination as the reason.

If one is given clear, concrete feedback ("We rejected you because you didn't come up with a simpler algorithm, and you lack experience with framework x"), there is little room for them to think they were discriminated against in any way but their skills/experience.

The issue is documentation, and the legal risks it can carry. If you get ghosted and believe it's discrimination, that is a very different beast than if you can twist the words of the feedback you've received to imply it may have been discrimination.

From the point of view of a company that employ many people who do hiring, someone is guaranteed to write something stupid. When people write code, they do bugs. When they write feedback, they do stupid.

Or even more likely, someone will inadvertly show his bias that could have stayed under cover. People are not that great in hiding their biases over many interactions.

We're dancing around a reason that the article misses: a lot of hiring decisions are discriminatory.

If they were confident about having processes with no discrimination, it would likely be advantageous to the company to show their cards and give the feedback.