The Mimicream repair works on any tool/weapon with durability, but the problem is that, for exemple, tinker armor allow to have pockets on them, allowing items to be inserted

When using the Mimicream repair mechanic, it copy the nbt tag and so DUPE the items in the pocket

Thankfully, tinker pockets are limited (no shulker/backpack) but there is still some problem with fairly easy dupe (if you don't consider the unfairness of mimicubes lol) and the fact that there might be other mods that would cause the same issue