Yeah I prefer the term "precaution principle", it's more straight forward because it describes the action instead of what's motivate it.

But known unknowns and unknown unknowns are not the same things though. known unknowns are a space you can account for. It's easy to put a number of it. unknown unknowns not so much, and dealing with it is more a matter of morality than science. You can't scientifically deal with something you can hardly define or quantify.