The acronym wasn't so much about 'the Big Tech' companies, more about 'Innovative tech companies that dominate, or are poised to dominate, their market'.
Also remember that the landscape has changed since the initial FANG acronym came into existence.
It was specifically a Jim Cramer-coined term for companies whose stock was hot at the time--which correlated somewhat loosely with both comp and dominance. Netflix is somewhat of an outlier in various respects and arguably Microsoft should probably be on the list today--even if the WA-headquartered companies tend to pay less than the CA-based ones.
Also remember that the landscape has changed since the initial FANG acronym came into existence.