The irrational part of this is that the 'wrench system' is actually sized in 32nds of an inch, and thus would be much easier to comprehend with 'improper fractions'.

4/32, 5/32, 6/32, 8/32 ... etc

Or just "size 4, size 5", etc, with the "/32" as overall metadata

Except that there are wrench sizes in the /64 range as well.

https://www.google.com/search?q=13%2F64%20wrench

Rather than 4/32, 9/64, 5/32, you'd have 4, 4.5, 5. That actually seems even better.

And then you can just use millimeters as the unit instead of the awkward "inch/64".

The irrational part is using "inch/32" as the unit instead of, say, millimeters.

Yep, there are many counter-intuitive aspects to the rational numbers. They're ordered just like the integers, and yet given any fraction there isn't a well-defined "next" fraction. But there are still "gaps" (irrational numbers). The same fraction has infinitely many representations. Despite that there are no more rational numbers than integers, yet the number of "gaps" far exceeds either of these. Not every fraction even has a finite decimal expansion. And fractions allow you to specify a level of precision for measurements that could never be achieved in the real world under any circumstances, which immediately raises questions about what these extraordinarily precise fractions actually refer to in the real world.

I honestly believe that lots of kids detect these issues on some level, but their curiosity and confusion remain unresolved, possibly for life.