If you're referring to the term "this code" in subsection (a), that entire subsection is in reference to "the speed of a vehicle upon a highway NOT in excess of any of the limits...", then no, that does not include you driving 15 to 20mph in excess of the maximum limit. Therefore it does no apply to neither 22349 nor 22356.
But judging by your last comment, you were referring to subsection (b) and in that case, and relative to the term "this code" in subsection (b), the two qualifiers in that subsection are "in excess of" and "prima facie speed limits", so that excludes you diving "in excess of" - "any maximum/statutory limit".
It isn't that difficult to deduce that neither subsection in 22351 would apply to "driving in excess of maximum/statutory limits", and therefore 22349 and 22356 are excluded!
(a) The speed of any vehicle upon a highway not in excess of the limits specified in Section 22352 or established as authorized in this code is lawful unless clearly proved to be in violation of the basic speed law.
(b) The speed of any vehicle upon a highway in excess of the prima facie speed limits in Section 22352 or established as authorized in this code is prima facie unlawful unless the defendant establishes by competent evidence that the speed in excess of said limits did not constitute a violation of the basic speed law at the time, place and under the conditions then existing.
1. So Cal is a part of a bigger entity called California... And unless you can establish a different set of laws for So Cal, you'e required to comply with the California Vehicle code!
2. We've already established that your 15-20mph in excess is NOT the norm anywhere in So Cal, in fact your specific example was "15 through Mojave and 5 through Pendleton" both of which are more rural, and in your other example you qualified it further by stating: "I'm not talking about the 405 through LA or anything here".
3. Some laws, and in particular "vehicle code sections" have been on the books longer than you and I can remember, and just because you'd like to think that society's perceptions with regards to safety have changed recently just because you are now a licensed driver and you like to speed, then maybe the laws are way behind or, the more likely answer is, you cannot force your opinion on the entire society.
4. If you think that speed and speeding are new concepts and that the laws have not adjusted accordingly, then think "hot rods" and the 1960's/early 1970's era where muscle, horse-power and smoking tires were the "in" thing.
I disagree, I think parents should grow the balls to have the ability to dictate and control what their children can and cannot do, instead of subscribing to the idea that "its OK for my kids to do it because everybody else's kid is doing it"! But that's just me!