Well, it does help for natural trainers (even if only marginally) - you might as well put your body in the most anabolic state it can be in.
I personally like carb cycling as when I was training to a highly competitive level (club-level rugby) the conditioning and endurance I got from that was hugely helpful. Then as I started to go down the powerlifting route, I found that keeping a decent carb cycle going helped improve insulin sensitivity which again translated in decent metabolic improvements. Albeit supplementing with leuicine (protein synthesis), creatine (ATP output) - I took part in an MSc study that Loughborough University were doing, and there were marginal but still recordable improvements.
However, yes, you are 100% correct, for most laypersons, and average joe gym trainers, it basically makes sod all difference. And exogenous insulin is so dangerous and I don't suggest anyone go down that route really.