There were already many duplicate abbreviations, so this isn't a new problem, and as you said, is a bad assumption, those systems would likely already be incorr

There were already many duplicate abbreviations, so this isn't a new problem, and as you said, is a bad assumption, those systems would likely already be incorrect. I would guess systems using abbreviations like this presumably are using POSIX timezones, which isn't going to be historically correct, but require defining all the information about the abbreviation/zone anyway (i.e. they are basically made up timezones, so it shouldn't matter).