"(b) If a vehicle is being driven at a speed less than the normal
speed of traffic moving in the same direction at such time, and is
not being driven in the right-hand lane for traffic or as close as
practicable to the right-hand edge or curb, it shall constitute prima
facie evidence that the driver is operating the vehicle in violation
of subdivision (a) of this section."
That section has numerous exceptions, as does the referenced "subdivision (a)." The point is there are many valid reasons why someone would come to a dead stop in the left lane of a multilane 2-way road.
On a limited-access divided highway there are far fewer reasons, limited only to emergencies, and the left lane can be legitimately considered to be the fast lane.
"(b) If a vehicle is being driven at a speed less than the normal speed of traffic moving in the same direction at such time, and is not being driven in the right-hand lane for traffic or as close as practicable to the right-hand edge or curb, it shall constitute prima facie evidence that the driver is operating the vehicle in violation of subdivision (a) of this section."
http://www.leginfo.ca.gov/cgi-bin/displaycode?section=veh&gr...
Says nothing about limited-access divided highways.