Maybe with a layer 7 attack, but not with a layer 3 attack. The author also described the difference between the proxy request and a legit request, so he can just block the proxy requests. Try using slowhttptest. You don't even need a botnet.

I think the article described a different response, but not a different request? Anyway they mentioned that some requests were cached, so you could request a cached object to avoid hitting the original host, if you wanted a level-7 attack.