combining items with enchants higher than normally possible in a anvil reverts the enchants to the normal maximum

What I expected to happen was...:
if you manage to get say sharpness VII or something, and you combined it with something else on a anvil, it should be able to be combined with the enchantment untouched (staying at VII or whatever level it was)

What actually happened was...:
instead, combining say a sharpness VII book you somehow got would result in it being sharpness V in the new item

Steps to Reproduce:
1. give yourself a book or item with say efficiency X or protection V
2. combine said item with another item
3. it shows the normal max in the other end, not the level it was set to
this was tested with unenchanted + efficiency X pickaxes resulting in efficiency V pickaxe