In the first bullet point of the linked document, there is an inconsistency in the very style it’s trying to enforce, namely capitalization. UUID vs Id. Consistency is hard!
Not sure why it is inconsistent to have UUID be all caps and Id be title cased? They feel different to me. But maybe I'm missing something.
Initialisms are pronounced by saying each letter in order. Acronyms are pronounced as if they were words.
"ID" is a funny case because it's an ordinary abbreviation, and not really an initialism* or acronym, but it's pronounced just like an initialism. I think I'd prefer it "ID".
I would definitely avoid writing it "Id", lest it be confused with Freud's concept.
* unless as Norm Macdonald joked, the "D" is short for "dentification"