If someone's communication skills are bad, it's legal to not hire them. That's a job-relevant characteristic. Of course you have to apply that job requirement to all candidates, not just OPT candidates.
Also you got to think HR has incentive to let it slide to get those cheap workers. It’s sad hearing them talk salary expectations of terrible candidates knowing they’re going to be hired because they want 20k less or whatever.
I’m just sorry for the people the candidate will be working with and the company itself because it’s a net negative for them.