Assuming the applicant has zero experience with gaming, this would be an incredible opportunity to evaluate how well they cope with uncertainty under pressure and adapt to unusual conditions. If the applicant is already a grandmaster on the ladder, this becomes an excellent test of their humility and teamwork.
If the applicant gets shitty about the mere idea of playing a game as part of a "serious" job interview, I think I would have all the information I need to make the right decision. If you can't get a little bit flexible in this new world, I don't want you on my team anymore.