[schmorptron]

Anti-Cheat is the only industry where security by obscurity is valid.

[tester756]

Obscurity is always valid because it increases security, doesn't it?

[nitrogen]

They're referring to this idea: https://en.wikipedia.org/wiki/Security_through_obscurity

Obscurity can be a layer, but it can't be the only layer, and in general systems (such as web servers) need to be designed to withstand full-knowledge attacks. That isn't likely to be possible when it comes to anti-cheat, so obscurity plays a larger role.