By this logic one might say that DD/MM/YYYY works for alphabetical chronological sort if you don't go between months...

Have another go at this train of thought, mate... You're basically saying "MM/DD" is better at sorting chronologically than "DD/MM", since the year part is taken out of the equation, which is already the established consensus, and not ironical whatsoever. And the ISO standard is already to use YYYY-MM-DD, so that's the winner IMO, hands down. Japan is simply following that but using a slash as the delimiter.

Excuse me, sir, but WAT?

When you search or do any stable sort, I would think you want your primary attribute to be the one with most finite values? That way you are front loading the pruning of the search space.

So it's actually on favor of Japanese style