After filling over 8 double chests with enchanted books that were obtained exclusively through my enchanting table, only a fraction contain level V enchantments, all of which are Impaling V. Every book was created using the most expensive option (3 experience levels). This seems to defy probability.

To be clear, none of these books contain Sharpness V, Efficiency V, Smite V, Power V, or Bane of Arthropods V.