It's not just that they're overengineered, they were often made out of cast iron instead of aluminium, and since production tech wasn't as good they had greater tolerances. Add in that lubricants has become much better during their lifetime ontop of that and you're there.
My engine is at 470k kms and was built in 1998, and has been well taken care of, and the bores are pretty much immaculate in that thing, and it's a B230 designed in 1974 with an improvement made in 1985 for better lubrication.