[Jedd]

> Initialisms are a subset of acronyms; acronym is accurate here.

I believe you have that inverted.

An abbreviation is a shortened version of a word or phrase, and encompasses both initialisms and acronyms. An initialism is pronounced one letter at a time.

Acronyms are a separate special case - an abbreviation that is pronounceable as a word unto itself.

[wizzwizz4]

> The broader sense of acronym inclusive of terms pronounced as the individual letters (such as "TNT") is sometimes criticized, but it is the term's original meaning[1] and is in common use.[2]

https://en.wikipedia.org/wiki/Acronym