I don't think that's the point of the article.
What I think it means is that, if I wanted to hire a janitor, I would not be able to reject an applicant just because the applicant has no high school diploma. (The point being that a janitorial job doesn't need a diploma, and the reason that they don't have, might possibly be because they have a disability).
The issue is that because some disabled people might not have high-school diplomas, the very act of asking for a high-school diploma where not absolutely necessary, could be regarded as discriminatory (whether an applicant is disabled or not).
Of course, if I could prove that job would require an employee with a high school diploma, that would be different - and I would be allowed to reject an applicant without a diploma.