IMO, and it's completely lacking in any kind of insider info... Most of the people claiming game lag are full of it. I know in RTS games like StarCraft there are hacks to keep you from being dropped from a game if your latency is really bad, but as far as a FPS game goes, it sounds like a load of crap a bunch of people tell themselves to feel better.
What most cheats in FPS games do is just kind of make the game far less fun for everyone except the cheater. If someone has a hack that gives them a headshot every time, that gets old fast for everyone else... But I'd have a hard time buying that it somehow introduces any added latency.
Something I find happening a lot of times is that someone will try and feign understanding about a topic they are hopelessly in over their heads on. Unfortunately, if said with enough confidence, people who don't themselves know any better will tend to accept it. You walk into some building,even if you have absolutely no business being there, if you LOOK AND ACT like you have every right to be there, most people will never question you. So you get a lot of strange ideas that are based on partially understood concepts at the best of times, and are complete fabrications freshly pulled from the neither regions more often than not, but because people say them with a certain confidence and conviction, people never question it. Also because these people probably know even less than the other person, but have at least heeded the part about not opening your mouth to prove you're an idiot when someone thinks you are.
All you need to do is look around at things like the near religious zealotry over things like firewalls and registry cleaners. When you really get down to it, and understand networking on more than just a "it lets two computers communicate" level, you realize that things like outbound filtering so touted by most third party firewall vendors is of dubious value at best. For the average user, something like the Windows firewall is just fine. It keeps out the automated probes social malcontents routinely run, and that's really about all the more people need. Then there's registry cleaners. When you learn a little bit about what the registry is, does, and doesn't do, you see the complete and utter lack of a need for any kind of "cleaning". If people just asked real simple questions like what exactly constitutes an "error" in the registry, this whole cottage industry would collapse. You'll note there's a complete lack of any kind of transparency about how these programs work. What criteria do they use for deciding what is and isn't an error? Is that "error" going to negatively impact the system in any way if left in place? Conversely, is there anything to be gained by correcting this "error"? No company will answer the first one, and the answer to the other two is pretty much always: No. Yet people flock to these programs swearing up and down about how great they are. Some can be forgiven for forgetting that Microsoft created the first registry cleaner, and very quickly yanked it from their website. It's been well over a decade now, and it has yet to return. That alone should speak volumes.
I could go on with several more examples, but I think the point had been made. Just because someone claims something doesn't make it true. I might be the world's foremost expert on say Microsoft Outlook to name a program at random. That doesn't mean I know squat about say the Amazon Kindle.