25^7 is 6 billion, and there are fewer than 200m people in Japan. That's enough for one character to essentially be error correction.

25^6=244,140,625 - I think I have seen estimates of 100,000,000 addressable entities in the Japan postal address system (a bit half of them being households, the rest companies,public buildings, various organizations and so on )

TFA says "seven-digit combinations of numbers and letters".

Yes absolutely. But my comment was just to confirm what you were saying about 25^7 (with one control digit) i.e. 25^6 would be enough to cover everything that is addressable in the system today. If we increase that to alphabet+ numbers 35^6, it is even more feasible.

Oh, I see, thanks for clarifying.

If my password manager has an option to not use similar looking characters when generating a password, it should be trivial to do the same for this system.

Given that this is Japan, they probably just mean digits 0-9, which are quite often rendered that way rather than 一 to 九.