Some good stuff there.
"According to CIP 308 and 7.62 are the same thing." Yes. It is a common fallacy that 7.62 is lower pressure.
The 300WM is almsot same pressure as a 308.
The broken bolt was caused by bolt thrust of an oiled round. An oiled 308 case would probably have done the same thing.
The text explained the danger of excess headspace at the bolt face. Excess headspace caused by a too deep chamber does not matter. Shooting a 308 in a 30-06 is a half inch of excess headspace. no problem.
My two #4 target rifles have each gone through about 20,000 rounds of 7.62 and 308 ammo. No idea of how many 303 rounds they fired as 303 target rifles - and before that, when in service.
I have only heard of two failures of #4s, both had a broken bolt or a broken lug. Now that I see this video, I realize that the break was probably a manufacturing flaw, not a case of the bolt wearing out or being over-stressed.
The big take away is to not shoot oiled cases or in an oily chamber.