Security through obscurity doesn't really apply to anti-cheat clients the way you're talking about. That's more something that comes into play when dealing with user security(storing passwords, managing permissions and things). To some extent any anti-cheat client has to be obscured in some way because seeing exactly what the client is doing makes it much more easy to circumvent whatever controls it has in place.
The main issue is that any client-side anti-cheating device is fundamentally flawed; it can't provide a guarantee of non-cheating, it can only help. As long as people maintain control over their own pcs they will always be able to circumvent anti-cheating tools (in theory if not in practice purely because the methods the anti-cheat client uses are not obvious).