It can go beyond just not learning anything, and into learning negative habits. For me "Gym" was the most dreaded part of my life as a young person, and was one of the few things in school I really hated. I was generally out of shape, and have some issues with my vision. Given that, all gym taught me was how to handle being belittled and insulted both by my school peers and by adults in authority roles, and I learned that I should avoid situations involving exercising and sports unless I wanted to be subjected to that. It's taken many years, and my need to deal with resulting health problems, for me to try to un-learn all that.

What really bothers me is that I actually enjoy weight lifting and a number of solo cardio exercises (rowing machine, exercise bikes, swimming laps). I knew this when I was young too. But with only a few-weeks-a-year exception, these were not a regular part of "gym". I feel like these kind of activities are far better to learn, as the can provide a life-long basis for regular exercise, and should be an all-the-time option. Combine that with the other health focused skills you mention, and you're going to have much better life-long outcomes then you will get by yelling at the fat kid who can't do a hand-stand.