I've never seen that acronym before. It is hard for me to imagine any way in which Netflix would be more similar to the other four than Microsoft.
edit: perhaps this is a regional difference; are you in the Bay Area? I imagine that Microsoft has less of a presence there, and perhaps Netflix is a bigger deal down south than they appear to be here in Seattle.
I had the same doubt when I first read FAANG (some time ago), and reached the same conclusion: it's not about the importance or size of the company, it's about the job market in the Bay Area.
edit: perhaps this is a regional difference; are you in the Bay Area? I imagine that Microsoft has less of a presence there, and perhaps Netflix is a bigger deal down south than they appear to be here in Seattle.