> Why not hopefully more? Less? Is mathematics this inaccessible to the other 99.9%?

I think it meant "hopefully at least 0.1%." (I can imagine someone who feels that it's hopefully at most 0.1%, but probably that person wouldn't be kindly disposed towards efforts to fool people into being interested in complex mathematical topics, as your parent seems to be.)

Maybe "hopefully" isn't the right word.

My point is that not everyone who understands barber paradox (in plain english) has to understand formal logic, and not everyone who understands formal logic has to become a mathematician. However I still believe the existing of the plain english puzzle is a net positive for humanity's collective mathematical comprehension.

Another way of considering that statement is diminishing returns on the utility of mathematicians.

Some is good, but more isn’t necessarily better.