This statement contradicts what the link says. The hypothetical discussed in the link is that household ownership of cars decreases by a factor of 2 because cars will be able to ferry multiple people around. That implies fewer total cars in existence, but more cars on the road at any given time due to added driverless trips to pick up the next person.
I don’t agree with the link, but I felt it needed to be pointed out. If anything, this is an example of how most media doesn’t come close to understanding the possibilities of AVs.