Why are you comparing the SF bay area to the city limits of New York? Better would be to compare SF bay area to New York Metro Area, which is far bigger than the SF bay area.
I originally had the same reaction as you, but reading the parent's comment charitably I believe he's getting at "the population of the entire Bay Area is actually comparable to the population of just NYC proper with it's much tinier (relatively) area)."
In other words, some people tend to think of NYC as "huge major East Coast city" and SF as "huge major West Coast city", but the sheer enormous density of NYC makes it actually on a whole other level than SF.
Even coming from the Midwest SF feels like a midsize city. I've visited SF, I considered doing the SF software dev thing, but SF just feels like if Cincinnati developed a tech sector.
Chicago's urban population is 8.66m, and the urban area is 2,200 sq miles. I feel like I'm in a city here. When I go to West Coast cities I feel like I'm in a giant (sometimes quaint and charming) suburb. There's no density.
In other words, some people tend to think of NYC as "huge major East Coast city" and SF as "huge major West Coast city", but the sheer enormous density of NYC makes it actually on a whole other level than SF.