Kit interactions need to be clarified

Going against a GAT team in TW with Hera’s omicron means that if a member of that team is stunned then it’s dispelled and then the enemy team is inflicted with buff immunity and healing immunity. Ok simple enough

However SLKR has a stun that can’t be resisted or dispelled. So by order of operations it should be stun applied, then Hera tries to dispel it, but then can’t because it’s a stun that can’t be dispelled and then Hera applies her debuffs…how is it a stun that can’t be dispelled, is dispelled?