This is an all or nothing fallacy; the standard is not 100% success. It’s bit like saying “all locks can be picked, therefore they’re useless”.

That’s not what we’re discussing though. We’re discussing if anti-cheat through obscurity works, and I’m saying if it did there would be no cheaters. Instead companies have to build technology solutions that also don’t work 100% but that’s beside the point.

What next - if philanthropy worked there would not be any poverty in the world. So let's stop all philanthropic actions.

Your logic does not follow.

There are certainly less cheaters than if there were no anti-cheat methods. To use OP's example, an open source urine testing procedure would be trivial to game. The same thing goes for open-source multiplayer games.