Custom enchanted books do not apply to weapons via anvil

Giving yourself an enchanted book beyond survival enchant limits and combining it in an anvil with a compatible item will set the enchant to the maximum survival level.

1. Give yourself and enchanted book that cannot be obtained via survival mode or creative inventory.
2. Grab its compatible item.
3. Combine them in an anvil.

Expected Result:

The items will combine with no problem.

Observed Result:

The enchantment resets to max survival enchantment limits.