I think you may have misunderstood my point, which is that peak performance is attained when a few drivers drive altruistically (as the author does) and the rest drive "normally". If all drivers choose the same behavior (all altruistic or all normal), then the system doesn't work as well. This is interesting from a game-theoretic standpoint.

The author says much the same thing on his FAQ page:

If EVERY driver was to constantly maintain a HUGE space regardless of speed, then it would probably cause problems. The merge-zones might stop jamming, but the capacity of major highways would be reduced. On-ramps would become choked as traffic backed up into them, and there would be slowdowns extending far out into the countryside.

It is, of course, a purely theoretical problem, since there is no shortage of non-altruistic drivers.