That's a little overblown, and indicates a little bit of a fearful mindset. Historically, across all sports, there are myriad examples of the best of the best all emerging from "training cohorts" where the best athletes train with each other regularly. In triathlon that's true with the mythical 80's San Diego cohort, Tinley, Scott, Molina, et al. They'd tear the shit out of each other on weekdays while training. Then on weekends while racing. Or with the various Sutton contingents. Brownlees, etc. The "rising tide lifts all boats" effect.

I think the notion of super-secret training strategies is a bit overblown. There's not a ton of mystery. And exposing your training in full to your opponents can be to your psychological advantage. If you can handle a higher training load than anyone else, make that public and demoralize them. Inspire them to drive themselves into the ground trying to handle the same load.

Part of productive competitive mindset is learning to compartmentalize "competitive rage" and not let it turn to general "hate" or paranoid fear that someone might learn something from you.