It's real, and Speck referred to it during his talk.
For the record, here's the newspaper coverage of Jeff Speck's library appearance. As a reminder, private citizen Robert Landrum videotaped the entire presentation, which can be viewed at one's leisure at YouTube.
Something to walk about in New Albany; Author talks walkability in crowded event in New Albany, by Daniel Suddeath (N and T)
... Most roads are designed for far more cars than they will ever hold, so cutting lanes to install paths for biking or walking doesn’t mean vehicle capacity will be reduced below existing use levels, Speck said.
He believes many engineers fall victim to “induced demand,” where they add traffic lanes that aren’t needed and believe they are vindicated when more traffic arrives.
Studies prove that when you add lanes and make it easier to commute on a road more motorists will choose that route, Speck said.
“In congested systems, the primary constraint to driving is congestion,” he said.