Duelling wand's spellslinger meta invocation can't be used to switch weapon

Was playing around with double spellslinger and noticed that you can't use the actual trigger invocation if you don't have the weapon already equipped.
It would be nice to be able to use it in the same manner as you can switch between two weapon sets for different spells.
Not sure if this is intended or if it was an oversight?

I was hoping to use the weapon swap spellslinger to add a non-projectile spell to my set up, but alas it does not work :( I was only gonna use 1 spellslinger too

Id also like to know when can we Dual Wield wands again as well