A logbook is also the official way of documenting FAA-countable flight hours in order to show qualification for FAA certificates, ratings, privileges and currency. And the FAA is entitled to look at that official record and take everything in it as written, without some oral singing and dancing from the pilot.

IOW, log ANYTHING that doesn't properly fit into the column you put it in and the FAA is perfectly capable of taking your "prized possession" and using it to revoke all your certificates and ratings under FAR 61.59.