Items Having Different Levels When In Inventory VS Equipped

[WFD1992 (Wylyth)]

For example, my Maliwan Hellfire is level 25 when in inventory, but when I equip it, the level changes to level 20.

[Piemanlee (Goodbye friends and not friends, it's been a fun ride)]

That’s becuase of weapon proficiency, only the lvl the item was when it dropped actually matters