Well, it something has to do with apple devices in the middle east.
In the middle east we use Hindi numerals instead of Arabic numerals. (strange, right?!)
I think apple differentiates between numerals in all languages. For example, if your password contains '1' in Hindi form, and you set it by an apple device, you will not be able to log in if you used the usual form '1'. This is not the case in Microsoft devices, where numerals are treated the same in the system.
My problem is that if a user enters a number (from apple device) using Hindi form, it will be displayed as special chars. For example, if you entered the number '8' in the Hindi form (https://en.wikipedia.org/wiki/Eastern_Arabic_numerals if you are interested) it will show ظ¨ instead of ٨.
Therefore Replacement Variables were useful.
I hope it is clear.