I always thought it odd that Netflix made the cut into that acronym but Microsoft did not. But I think people colloquially add Microsoft to that mix even if it isn’t literally in the acronym.
Netflix doesn't quite belong with the others but FAAG is a more problematic acronym and FAAMG isn't pronounceable.
I've also seen GANDALF (google amazon netflix dropbox amazon linkedin facebook), but dropbox probably doesn't belong in that list. There's plenty of backronyms, but one ends up just hitting critical mass.