The CA law you cite is applicable to CA residents ONLY. Here is the law that applies to you.
DRIVER LICENSING for DOUBLE TRAILERS - NONRESIDENTS
12502. (a) The following persons may operate a motor vehicle in this state without obtaining a driver's license under this code: (1) A nonresident over the age of 18 years having in his or her immediate possession a valid driver's license issued by a foreign jurisdiction of which he or she is a resident, ....
In summary, nonresidents may tow two trailers with a non-commercial license IF their base state allows it. However, they would still need a valid medical certificate per 12502 CVC.
Only 4 states of the 39 that allow double tows, require the 1st hitch to be a 5th wheel and CA is NOT one of them. Also, one of those 4 has defined 5th wheel in such a manner that a pinned tow bar fits the description. Also, many states only have length restrictions in their commercial vehicle code, not the standard vehicle code, so you must check that very close. CA is hard nosed on the 65' length and I have seen a citation for 18" over.
