They have only a handful of flights (and simulators) that are meant to represent a cross-section of pilot training. It gives them more credibility as flight surgeons when they're giving you an up chit or a down chit when they have sat at the controls of a helicopter on a low level nav route, tried to land on a night fam (the lit spots at Santa Rosa OLF are sort of in a black hole... I had a few manage to maintain control down to about a hundred feet but that was the closest we ever got), been upside down in a T-34 or a T-6, been in and out of clouds in turbulence, and experienced the sensations that come along with those aspects of flying.
The flights could be stressful but I thought they were tons of fun. The IPs don't really expect the student FS to brief the oil system, expertly explain the nuances of aerodynamics, or anything like that. I always treated the flight physiology briefing items as a cooperative discussion. We'd discuss maneuvers and the procedures for them but in the context of how your brain knows to make your hands and feet move the right way and what mistakes your brain can make that result in the wrong control inputs. I'd usually get the FS in an uncomfortable position in the flight, but do it in a safe, controlled environment, which was kind of the objective of putting them on those flights.
Like that black hole effect on final, if one of my student FSs felt that for himself or herself in the safety bubble of the training command, then so much the better. That experience sharpens their judgment in the future, to confidently tell one of us aviators "no" when it's a tough call and it's the right call. Just as important, those experiences give the FS that much confidence to sign us off when we're back in good shape and aeromedically ready.