They state they are a hiring manager. If they can't manage difficult but productive employees, they may need some aid learning how to manage effectively.

It's very easy to manage them: don't hire them. Bringing on someone who is a disruption to an already productive team because they seem like they may be a good individual contributor, based off the extremely limited exposure you have had to this individual, is a bad idea.

It is exceptionally easy to manage when there's nothing to manage. At that point, managers are superfluous, and the company is wasting money and not maximizing their profits that could benefit from a good manager working with excellent contributors with imperfect dispositions.