Scuttle Silence Inconsistency

So I am under the impression that a Silence will remove the Rift Scuttlers "shell" as hard cc does. As far as I am aware, there are 7 champions that have a silence (or micro silence in Kassadin's case).

Of these 7, 5 of them do remove the scuttle's shell. 2 of them do not; Soraka and Cho'Gath.

Soraka I can understand as her E does not harm minions and neutral monsters.

Cho'Gath's W does do damage though but fails to remove the shell.