Audiobooks always sync on iPod classic/iMac M1

when I sync my ipod classic (gen 6) to my imac (M1 2021) over 100 audiobooks always are included in the sync, even though only 1-4 books have been listened since the last sync. The iPod is config'd to sync "selected audiobooks" ... 165 of 300+ books in my library. My audiobook files are .m4b format. This only seems to be happening with audiobooks - my music seems to sync properly. What all this means is that syncing takes a really long time (sometimes over an hour) when it should only take minutes.