That's 14 CFR 61.51(a)(1). Subparagraph (a)(2) covers "aeronautical experience required for meeting recent flight experience requirements of this part," which would include 14 CFR 61.55 and 14 CFR 61.57 landing and instrument currencies. So if you want to be able to carry passengers or fly IFR or act as a required SIC (other than a safety pilot under 14 CFR 91.109(b)), you have to log the necessary recent landings, approaches, holding, etc., even if you aren't using it to meet requirements for a certificate, rating, or flight review.
Me, too.
Sorry, you're out of luck -- it isn't written in either document. For FAA purposes, you need only log what's needed for certificates, ratings, flight reviews, and recent flight experience requirements. If you cover those requirements, you've done as much as the FAA requires.
However, insurance companies may require documentation of more flight experience than the FAA. Some require some minimum number of hours per year, or in type, or complex, or multi, or whatever, or give reduced premiums for higher levels of experience. If it isn't in your logbook (or you can't produce your logbook -- see the discussion about "company records" above), the insurance company will take the position that if it isn't logged, it doesn't exist. Further, if you claim experience that isn't documented in a form acceptable to the insurance company (or a jury, if it comes to that), you could find your insurance policy based on that undocumented time being null and void -- after you have your accident.
Choose wisely.
