The enchanted book unbreaking V and up are not craftable. Its is possible to do it on a item but not as a book after getting unbreaking 5 on 2 tools and trying to combine them its returns to unbreaking III

This bug report seems to be incorrect. It is combination of enchantments on items only that seems to be inconsistent with book enchantment uncapping. I can reproduce with any enchantment on an item while trying to combine two enchanted items with multiple different enchantments- the enchantments will always be max vanilla level in the output.