Yeah I understand and maybe they are not hammering out the sheets to a uniform spec within specified naval tolerances (some sections too thin/thick) but if you read about 'cheap Chinese steel' and the problems manufacturers have with it, it begins all the way back at the crucible and the presence of contaminants/impurities which impacts the crystalline structure of the steel and creates weak points. Like I said it's a difficult and complex process that uses a ton of energy and can go wrong at many, many points. Get the iron/nickle/carbon ratios wrong, your ingot is fucked. Too slow getting the ingot to the rollers, you have scaling/oxidization and your ingot is fucked... The navy probably demands very specific tolerances for tensile strength, elasticity, thickness, etc. I don't think it was "lets make it .5cm thinner than specified to save cash across the board" and more "fuck this came out .5cm thinner than specified, let's just ship it anyway" or "This has too much carbon and is too brittle but nobody will ever know."