This is a bad hill to die on for a ux conversation. "10% can feel kind a big number when 100% is huge" is a funny argument, as is trying to be pedantic about "nobody knows" as a shortcut for "most people won't know and you can't rely on any particular user knowing". If 10% is big enough to matter I can't wait to tell you about 90%!
> "10% can feel kind a big number when 100% is huge" is a funny argument
That would be a funny argument if it were the one being made.
I'm not suggesting that one would design for the 10%, but I also think that writing off 10% - "nobody" - (particularly of a large number of people) is pretty dumb too.