Enchanted books from fishing

I started a single player world in one of 1.18 pre-releases. I do a lot of fishing with a fully enchanted fishing rod (LotS/L3/Ub3/M). Before final update to 1.18 I could get ca. 3 books/play hour. After update, I get none or just one, as if LotS =0. Frequency of other loot (enchanted rods bows/fish/junk) seems not to be affected.

I wonder if it is a bug/work as intended/just bad luck.

Fishing in open water, warm ocean, no AFK.

Also, I wonder if enchantments are really random since some appear with much higher frequency than others.

 

What I expect: same frequency of fishing enchanted books as before update

What I experience: very low frequency of fishing enchanted books after update to 1.18.