Let's say you hired me to be your basketball coach. So, I took you out to a beach, gave you a volleyball and began training you in playing volleyball. Would you keep me as a coach?
Running and jumping in sand is more difficult than on a basketball court. A volleyball "pass" is sort of like a basketball jump shot. I could even have you play a basketball game, and even if you should do well, would you still keep me as a basketball coach?
Of course not (at least, I hope not). Fundamentally, I would be teaching you a different game --- volleyball --- not basketball. That's the point I'm making. If students are never subjected to anything that has some correlation between self-defense or combat, it's disingenous to suggest the training perpares them for it.