Are digits represented in sequence in all text encodings?

Question

This question is language agnostic but is inspired by these c/c++ questions.

How to convert a single char into an int

Char to int conversion in C

Is

Answer 1

You're going to find it hard to prove a negative. Nobody can possibly know every text encoding ever invented.

All encodings in common use today (except EBCDIC, is it still in common use?) are supersets of ASCII. I'd say you're more likely to win the lottery than you are to find a practical environment where the strict ordering of '0' to '9' doesn't hold.