Me personally...I don't like to work out in the evenings because of nutrient timing. It probably doesn't make a whole lot of difference, but I'll explain why. If I work out in the evening, then the odds are that I'll only get in a meal or two after my workout.
An ideal situation (which happens more frequently) is where I'll work out in the morning. I'll eat a meal or two beforehand. After that, I'm able to spend the rest of the day eating for recovery & then growth whereas if I had lifted in the evening, then I would be going into a catabolic state soon afterward (also known as sleep). I'll have a carb/protein drink PWO & then have a very high protein (& low fat) meal immediately afterward. I think that the first PWO meal is the one where your body can use the most protein. I'll successively ramp down protein consumption each meal from around 60g to 30g. At every meal, I try to take in a minimum amount of protein because my body is growing all day. There isn't a lot of point in trying to hit EXACT numbers like that IMO. Just make sure to provide your body with what it needs & you'll be fine. Hopefully that clarified maconutrient differentiation between meals. It's all about necessity. And if you don't care about nitpicking, then don't. You and I both know a lot of lean &/or muscular people that have never heard of the GI or insulin.
Insulin is a pretty cool hormone. You want your insulin levels steady. Following a low GI diet will do that for you. Exercise will elevate insulin levels. Obviously, exercise isn't going to cause you to store fat.
(not directly) Insulin is a very important hormone. You should be worried about how your body is going to store these high GI carbs that you would take in PWO. As long as you take in a reasonable amount & the correct stimulus is there, then your body should store these as muscle glycogen. Think of carbs in your PWO shake as "priming the anabolic pump". I believe that's how John Ivy refers to it. It's setting the stage for growth...it's very important. It increases nutrient uptake, prevents catabolism, prevents gluconeogenesis, etc.