if it turned out that what you quoted was not a regulation at all, my logs might still be worth keeping.
Well Captain EXDAC you have the source. Read the FARs carefully, you may be able to avoid the trash can after all. The regulations make it very clear that the rules regarding completing the log book are distinct from the flying regulations. To repeat:
Under U.S. FAA FAR 14 CFR 61.51,[6] logging flight time as a PIC is different and distinct from acting as the legal PIC for a flight. In general, the PIC of a given flight may always log his or her flying time as such, while other crew members may or may not be authorized to log their time on that flight as PIC time, depending on the specific circumstances and the controlling jurisdiction.[7]
The regulations are ICAO; the overall authority, but each NAA can file a difference as it sees fit. However the FARs and ICAO are almost synonymous. At least EASA thinks so.