Uther's Devotion Aura (possible bug)

Was playing QM just now and our Uther pointed out that he couldn't use his Q while standing in Stukov's silence in spirit form. This is probably an unintended interaction and I suspect it's a bug-Uther's spirit form is describe as being invulnerable, so silence effects should do nothing.

Does this seem like a bug? There's few enough silences in the game that perhaps this is working as intended, and I've just never seen ghost-Uther silenced before.