Offhand not included as part of the players inventory. For example when checking for a cost item.

[LihP]

Not sure if there is a good reason for this, the same might be said for armor slots, if you are wearing something that is a required cost item. Think these slots are also not checked when using the hasitem or hasitempresise modifiers.

Magicspells 4 beta-7 Paper-1.16.1