I agree, that’s why I said, “… they simply don’t use the units enough.”
I know imperial VERY well, but that’s because I lift weights listed in lbs and craft things all the time, which takes measuring. I also do 3d printing in metric, so I have a solid feel for millimeters, centimeters, and decimeters, but less so full meters because I seldom work on that scale.
Considering I had an intuition for lbs as a child, though… I don’t really buy that people suck at their native units as adults. If they do, they’re simply not paying attention.