Right. Every circuit is an IG circuit when wired with non-metallic components.It could be for an IG, if they used a plastic box on the other end the EGC would already be isolated.
It is 4 conductors or more commonly called three wire with ground.Where do you see 4 conductor NM?
I don't believe an EGC can be anything other than bare, green or yellow with a green stripe. And you cannot reidentify anything that small with green tape either. So it doesn't belong there.