So, it seems that because Iono (unlike the other hybrids) doesn't have the restriction of NOT wanting to be put in the box, can be added to the party then deposited to the box indefinitely, allowing for dupping.
Uppon further testing I found it's not really "duplication", it's quite literally the exact same Pokémon (If something happens to one, it happends to the other one), just appearing more than once.
Would be funny to see how this works in double battles