This sounds reasonable. /s
Do you have an example of anything that accounts for the possibility of unknown unknowns? My guess is if you do, then all it will take to "debunk" it is someone with a bigger imagination.
EDIT: bad comma
It's actually quite the opposite.
You start from what you know and what you control. From that you can assess what you can mess up. The scale, the consequences and likelihood of it.
E.G: if you are using a very potent instable new explosive, you have much more unknown unknowns that if you are manipulating a well well know concentrated acid.
Now starting from here you know what the cost of what you don't know could be, and else can choose measures to mitigate that such as more research, bigger safety coefficient, additional staff, insurance, etc.
When we blame a company for not taking in consideration unknown unknowns, it usually means they just tried to build the very minimal legal requirement to put it on the market and make money. They may have known that it was risky, but they didn't bother.
Perhaps this is just semantics but I have always thought of "unknown unknowns" as being in that mirky realm of "every single possible thing".
Perhaps I should have been more charitable and less pedantic, which is honestly hard for me to do when I see someone passionately argue against something I thought was a scientific consensus.
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.