Mending Enchantment Doesn't Work on Iron Sword

My Iron Sword was Badly Damaged, but it has mending enchanted to it,

So I Used 32 Bottle o Enchanting (Experience Bottle) to try and fix my Iron Sword (renamed; Excalibur) and it Doesn't Work as well as having Unbreaking 3 put on to it,

However I only Noticed it on Iron sword, It might possibly be Affected on Other Tools