Don't believe a word of it. There must be a harness in there, testicles aren't attached by very much at all, there's no way you could pull 12 tons of cars with them, they'd be torn off. I doubt whether a penis is well enough attached for that either.
And no amount of Foo Kwung Dung or any other sort of "training" is going to strengthen those parts as they are not muscular.
Physiologically impossible hooey.