If you're research show's that high GI carbs don't up your GH levels then you're probably right. But that's not why carbs are important after workout, and doesn't change the fact that carbs will fuel your body much faster (and better) than protein after high intensity exercise.
If all you eat is protein after workout than you're defeating the purpose of the post-workout meal. After workout, your body is starving for energy because it's glycogen (energy on demand) is depleted. Your body has no functional use for protein at this time, so consuming it after workout will be no different than simply waiting until your next meal. Right now, you're body is in a panic state and it's number 1 priority is to replenish your glycogen stores for energy. This is a survival tactic. Your body needs that energy for possible defense, fight or flight, etc., and will do anything to get it, and that means breaking down fat or muscle tissue, or both, and probably not in the order you'd like. If you don't want this to happen, it is your job to supply your body with the resources it needs to refuel itself.
For those of you reading this who might not know, glycogen is essentially glucose that's stored in your muscle tissue for secondary energy. Hi GI carbohydrates pretty much go straight to your blood stream (glucose). This higher blood sugar will naturally create an insulin response, which in turn shuttle's the glucose to your muscle tissue to be stored as glycogen. So basically:
carbohydrates --> glucose --> glycogen
However, your body processes protein and fat much much slower than carbohydrates (even fast whey proteins can't keep up), and by the time it has access to those resources your body will have already taken its own measures (not good). Even if that weren't the case (because I know I'm gonna get a protest regarding the absorption rate of whey), eating protein or fat as a post workout meal would still be pointless, as neither will have any significant effect on your blood sugar, nor will there be an insulin response to transport excess blood sugar (which you don't have, because all you ate was protein and fat) to your cells.
This is why I eat nothing but high GI carbs after workout, and save protein and fat for my next meal. By no means do I claim to be an expert, but I have yet to hear any solid explanation as to why anything else would be more effective.