I dunno, I don't have my B.E.E., so I don't wanna start a long *** debate, but I don't think everyone uses the same AWG standards...
I've had 0/1 and 4 Guage from 5-6 maybe more Suppliers of wire and some of them reallyvaried in size... I'm not talking about just the shielding...
EX... I used to use/Buy a lot of Phoenix Gold wiring, but they are pretty proud of it and its hard to find... Usually 5+ a foot for 0/1...
My friend Ricky was redoing his sytem and bought a load of some 0/1 from another know (not noname) vender, I though it looked a a bit Skinny... So, we decided to compare, when I stripped back the shielding on the PG leaving bare copper, not only was it thicker than the other Copper, it was thicker than the other wire with its shieding on...
I can see a lil difference from Roll to roll and brand to Brand, but dang....