This is why, many of the older guys in the industry like my Dad, when OEMs started to change to metric in the late 70s,
fought it tooth and nail and complained to the powers that be.

Because his associates and he knew the finer increments of metric fasteners would allow Engineering to eventually reduce mass and cost to the point vehicles
would make it to 3-36, and after that...."hey, who cares? Make money from parts and service! Not our problem anymore".

This is what we have to work with....Iron manifold, aluminum head, tiny metric fasteners.
Think about expansion/contraction, hot/cold, over and over.
It's just a [censored] combination.

If those fasteners were 3/8" grade 5 or 8, think they'd still break?