I agree that the split of full body works well, but I think that doing 4 sets each of flat bench and CG bench every 2 days is too much.
Bodybuilding is very personal, we all have different body types, and different genetics. So what may work well for you may not work well for him or for me. There are very few universal things in bodybuilding. Granted creatine seems to have no nonresponders, but there are people who refuse to take it because of bathroom related side effects
Some guys struggle to gain 5 lbs. I have to struggle to not gain 5 lbs.
You are no more entitled to your opinion than I am to mine. Thats the real point of these forums, so that different points of view are available. It only takes one workout plan like yours that leaves a guy feeling sore 24x7 to discourage him from bodybuilding entirely
And are there scientific studies to show that this sort of workout scheme builds bench press strength? since you say there are no scientific studies showing that a length of time is required to fully heal muscles.
Thats the beauty here, he can get opposing points of view, have people help give him new ideas to try. He still needs to take all that any of us say with a grain of salt.
Heck, maybe at 15 he can bounce back that fast inbetween (I know theres no way I can), but I think he should be prepared to give up the workout scheme you suggested if its bothering him from soreness after a couple weeks, and go to something with high intensity on workout days, and more time between.