Yes, this is a thing. The existence of a citation format isn't a blanket endorsement of its use in all ways in a scientific work. For example, in linguistics I

Yes, this is a thing. The existence of a citation format isn't a blanket endorsement of its use in all ways in a scientific work. For example, in linguistics I could cite a specific usage example from a (non peer-reviewed) webpage. On the other hand I wouldn't want to cite a (non-peer reviewed) webpage that outlines a specific linguistic theory.