I could see where it would be a problem, but it's not much of a problem for me. I have a metric dial gauge I can figure them out with if they ever did get mixed up.
Also to my eyes .5mm is huge so I'd probably notice if I did have a mix up and grab 2 different sizes.
I wrote the sizes both in number and measurement on the clear case with a Sharpie for that day the case gets accidentally dumped comes.
I have more problem knowing which cable I'm dealing with, I guess I can't spot an 8" difference
I was surprised they don't have a number stamped into them.