Even if SF's population "skews older" than Manhattan's, it doesn't refute the original commenter's anecdote. Older people in SF may dine out less than older people in Manhattan do - perhaps for financial or logistical or cultural reasons.
Manhattan has fewer young people with the means to dine out frequently. It's full of young people who want to be artists, fashion designers, etc... Most people who can afford fancy restaurant meals in Manhattan are older, more established in whatever their chosen career.
SF has a larger percentage of young people who are already wealthy (or middle class) from tech the sector. And thus more young people there dine out, more frequently.