Maybe the difference is now more subtle... which acronyms, when spoken, would you pronounce as a word (i.e. NASA) or spell out (i.e. MP3) vs the ones where you would expand them (i.e. Harden the fuck up). I mean... who actually says "H T F U" rather than "Harden the fuck up".
You mean where the "acronym" is not an acronym, but an abbreviation.
It's hard to scream for "no exceptions", it is language.
Quite - this is English. It's all about the exceptions and irregularities.