Yeah, it seems she just wanted to attribute all that to Ni when it could really be enneagram 6. Those are pretty enneagram 6y.
Yeah, the thing about 6s being most common is hear say so I'm not sure myself. In MBTI, most of the population are said to be SJs and most SJs are said to be stereotypically 6s so I guess that's where the idea could have came from.