Nah, I've punished my AirPods in the gym and they still work perfectly. I have been drenched in sweat and even had them rained hard on when running outside and they still work perfectly.
Yeah, at this point, I’m convinced it was something else. Perhaps something with iOS 12 beta. Mine are now back to working fine. I’m still running the beta, but maybe it had to do with the version running at the time. Who knows, but think I just jumped to the wrong conclusion.
Regardless, I found out that I like a different set of earbuds for working out and save my AirPods for everything else. Cost me a few bucks, but it is worth it.