At least observed in All Of Fabric 7 ver 1.20.1, enchanting seed does not reroll upon enchanting an item or book. This renders enchanting effectively broken, as you are unable to obtain any enchantments your seed did not initially roll you. Seed does re-roll upon server restart.

Edit: FSR Adding a tome to the enchantment library also changes the seed, however the existence and proximity of one has no effect on the static-ness of the table itself.