Since a "freeway"is included in the term "highway" I suspect that section was redundant and was incorporated into 22400:
22400. (a) No person shall drive upon a highway at such a slow
speed as to impede or block the normal and reasonable movement of
traffic unless the reduced speed is necessary for safe operation,
because of a grade, or in compliance with law.
No person shall bring a vehicle to a complete stop upon a highway
so as to impede or block the normal and reasonable movement of
traffic unless the stop is necessary for safe operation or in
compliance with law.
Apparently 22520 was repealed in 1997. I do not know why.