His premise there was "why simply adding more lanes won't fix the problem of congestion". He didn't claim that it won't lead to more cars using the road.

The problem with this is that if your goal is to build a liveable city where people can reach their destinations in predictable time without pulling their hair out, simply building more lanes does not usually help, for the reasons outlined very clearly in the article.

And that isn't exactly a wild guess, we have decades of data on the subject.