Investigative journalism wasn't a casualty of the 4th Corporate War. During the Time of the Red, Trace Santiago kept the tradition of the crusading reporter alive. Day 327 of #countdowntothedarkfuture.
Night City is said to be very vertical, with many people living in or around the corporate buildings, also have to remember that people have moved here from cities all over the country, not all of them joined up with nomads. I think it is a slightly exaggerated figure myself, but corps, news organizations, or even government could possibly benefit from inflating the numbers.
With robotics and bio-engineering HEAVILY influncing food production less rural population is needed to support cities. The assumptions of better economic opportunities and the "danger" of roving nomad/gang packs make living in the city very inviting.