that calorie plan makes no sense. 1g protein per 2lb of bodyweight would be about 100g protein for me. 60-100g of carbs. that means, at most, he's suggesting 800cal from carbs and protein. limited fat intake means what? 50g? that's another 450cals. so 1250cal total. per day.
this is the problem when everyone talks about how many grams of this or that you need. it ignores total caloric intake. those extra calories have to come from somewhere, but arnold is saying ALL THREE macronutrients should be kept low.
You're right. It doesn't make sense. I don't care what Arnold says, I know FIRSTHAND I'm not growing on 115 grams of protein per day.
With that said, what Arnold is making is RECCOMENDATIONS. They aren't set in stone. He'd be the first to tell you, not to do something simply because it worked for someone else.
When he first came to America and was training in Vince Gironda's gym, he was doing tons of preacher curls. He did such, because that was what Gironda's star pupil (2-Time Mr. Olympia, Larry Scott) did to get his huge arms.
But, Arnold said preacher curls didn't so as much for him, as they did for Scott. So, he went back to the basic barbell curl and cheat barbell curl.
You also have to keep in mind things like age, level of activity outside the gym, and digestion issues.
About 17 or 18 years ago, I was eating well over 300 grams of protein per day. But, I was walking up and down hills in college, carrying books to class. At times, I had to walk or run to destinations if I missed the bus. During the summertime, I played softball with my church league, pinch-running for the overweight guys on my team with bad knees. Heck, I ran for guys on other teams (except the one my team was facing, of course). That was the fun part of playing ball, back then.
Doing that, along with my weight training 4 times a week, allowed me to burn up that much food and still (for the most part) put on good size.
Gironda gave me the idea of making old-school protein shakes, with the dozen eggs and half-n-half along with a little protein powder. Back in college, I simply cut that into two batches. I drank one (six eggs 16-oz half-n-half, which I later replaced with lowfat milk) for breakfast before class; I drank the ohter before bed. During the rest of the day, it was either regular solid food or Mega Mass 2000 (to be later replaced with N-Large).