alt Hacker NewsI think it's more that "Some human some time has known how it works", not that "Any given human knows how it (all) works.".
But yea this glosses over a bit trial-and-error designs and, so to speak, "genetic optimization" kinds of designs where we just try random stuff and say "Hey, this works. Not sure why, but it works.".
There was a period of a century or more where steam engine design parameters were determined by experiment and gut feel. The physics of fluid dynamics required to explain why a design is optimal just did not exist yet.
There's a lot of places in history where engineering far outpaced the science required to explain it.