You should question EVERYTHING Tom, I do
2gms per lb is a measurement I read about 30 years ago in BB magazines
Anyway I do my own research, real world stuff.
Nearly 3 years ago I had Max and Dim training side by side in the gym, same program
They were having a race to a 100kg bench press, both weighed around 68kg
Max's eating was perfect, Dim was 25 and not paying much attention to nutrition, regular guy with protein drinks and 3 meals a day, I'd say around 200gms of protein a day
Dim beat Max to a 100kg bench by about a week.
Three years later Dim still eats the same, though he weighs 78kg. Max weighs 85kg. Dim benches 107.5kg on a very good day. Max has continued to increase his protein as he got heavier. He now benches 155kg
They train in the same gym, same programs, same coach, only difference is diet and lifestyle
I dont need a book or a lab coat to tell me where the difference lies
I am very priveledged in that when I give advice I have hundreds of lifters to draw experience from, most only train themselves
I reckon 50-60gms per meal is a good amount to start with
Max cooks 3 steaks every morning after eating 5 eggs and 5 bits of bacon for breakfast, washed down with a home made get big drink. He boils a pot of potatoes and has steak and potatoes for meal 2,3 and 4, peanut butter sandwiches next, protein drink during training, dinner at home, more milk before bed
If Dim did this, he too would be benching upwards of 140kg, but he doesnt