Trying to accomplish security through obscurity?
Yes, and like all black-and-white arguments, this one is getting pretty stale.
Renaming your admincp directory to something else is a meaningful, measurable deterrent. It means you will waste precious minutes or hours of a hacker's time just trying to find the front door before he can even get STARTED trying to break in.
It's no different than changing the listening port for SSH on your server, and making it not pingable, and I see that advice in every article I've ever read about hardening a Linux/RHE server.
Relying too much on any one type of security is foolish. It's why I don't use absurdly complex passwords with punctuation like ( and ", because it misses the point that your password is more likely to be stolen not because it's not sufficiently complex, but because of other factors.
If you use the same password on multiple websites (as 99% of users do), and one gets compromised, then a hacker will try that password on random websites (including your bank) to see if you used the same info. And we haven't even mentioned your computer being compromised by rootkit, virus, or keylogger. Yes some people use their name, the name of their cat, or 123456 for the password. But most people getting hacked aren't getting hacked because they didn't use enough punctuation in their password.
Putting the biggest meanest padlock on your trailer won't help if they have a flatbed to haul the whole thing away. But if your trailer is also chained to a pole sunk in 3 feet of concrete, and also has Lojack, well you can sleep easy.