You're not paying attention.

We are talking about two separate cases. One is with light traffic, the other is with a steady stream of traffic.

In the first case, light traffic, you generally stay in the assertive primary riding position for visibility, and move aside temporarily to the secondary riding position to allow faster traffic to pass when they approach, moving back out to the primary when they pass. Needless to say, except for the bike lane supporters out there, if moving aside causes drivers to try to squeeze in and pass too closely, then you don't move that far right next time.

In the steady stream case, where you maintain your secondary riding position, there is no moving in and out, of course, except for the occasional adjustment to the left, with merging (which includes negotation if necessary for you bike lane supporters out there), if traffic is passing too closely (or, of course, if there are obstacles in the way, etc.)

Make sense?