The argument against security through obscurity isn't that it doesn't work at all. It does to a degree, only it is not as strong as people think.

An example from the meat world: not publishing your vacation dates well in advance for the world to see somewhat reduces your chance of being burglarized. That is security by obscurity; not reliable, but not completely inefficient either.

But if you live in a fortress (security by key material), you can well declare your vacation dates without running the risk.