tier 4 mods in this artifact just don't appear anywhere in your armor slots as options. says the bottom three are "class item mods" then you check all slots in your class item and the mods aren't there.
#Artifact mods bugged and not slottable?
old pelican
radiant coyote
Yeah they are bugged, currently only slottable on artifice class armor right now. They're working on it.