You’re right that it is an initialism, but you’ve got the inclusivity backwards. Initialisms are acronyms that are not pronounceable, but they are still acronyms whether or not they are pronounced. You did get me questioning my own memory, so I looked it up to double check:
Sometimes, initialism or alphabetism is used to refer to acronyms formed from the string of initials which are usually pronounced as individual letters, as in the FBI (Federal Bureau of Investigation).
AFAIK acronyms are initialisms that are pronounceable
You’re right that it is an initialism, but you’ve got the inclusivity backwards. Initialisms are acronyms that are not pronounceable, but they are still acronyms whether or not they are pronounced. You did get me questioning my own memory, so I looked it up to double check:
From Wikipedia:
Hmm. Well, Wikipedia’s editors seem to think the opposite. We need reliable sources to sort this out now!