When the "Villager Trading Rebalancing" toggle is on, librarian villagers will never sell max level common enchanted books (except for one level only enchantments). In java common enchanted books can be max level enchanted so i believe this is unintentional.
This is easier to test on savanna villagers since you can only obtain curse of binding (1 level) and knockback (2 levels). You will see that you can only get curse of binding and knockback I.
Comments 2
@unknown: As info, it was previously reported in 1.20.35.25 Preview and 1.20.40.20 Preview. Since it wasn't fixed until 1.20.50.20 Preview, it must have affected 1.20.40 and 1.20.41 retail releases, although those were not added to the Affects Version/s list because nobody happened to mention it. In cases where a retail release is affected, we wait until the fix makes it into the retail releases before we resolve and close the ticket.
Note: Although it was technically fixed in 1.20.50, the update hasn't yet become available for Windows. This is unusual and likely means there was a problem loading the updated version into the Microsoft Store. Mojang has no control over the Store–that belongs to a Microsoft team–but I expect the problem should be resolved soon.
This says it was fixed in the 1.20.50.20 preview but it is still open