Originally Posted by JasonR

I can’t find exactly what you’re looking for either, but I can point out a couple things. Start with 61.3(c) which explains when a medical is required. Simulators are not mentioned, only aircraft. Check out 91.1089(c) which discusses check airmen and instructors in sims, and specifically carves out the medical even if acting as a required crew member.

I’m headed to FSI for recurrent soon, and they list a medical as a required document to bring. Best bet (short of getting in to see the AME) is to contact the director of training and/or the training partner being used and ask. The training partner is ultimately the one who will decide if your friend can sit for the check rides.