Dreadblades Transmog Question

Anyone know how to transmog the dreadblades appearances on daggers as sub? I saw that one rogue who 1 shots people on EU doing it. Can’t seem to make it work on sub.

All I can think of is if a Sub rogue has a sword in his offhand he should be able to mog his offhand into a dreadblade and his main hand into the sub dagger.

IDK of any other way since I thought daggers/swords were still restricted from each other. Someone else might have differing information if there is some cloak and dagger trick to it.

Maybe he was using iMorph?

I saw it from someone else’s perspective and it’s also visible on his armory page.