A troll is just someone who says something to provoke a (usually negative) response. They don't have any agenda other than to entertain themselves.
A dude going into a Fortnite community to post "Fortnite sucks ass" is a troll. A dude posting propaganda to sway opinions toward a political goal/shill a product is something else.
I suppose they're using the term troll to refer to a person engaging in behavior calculated to evoke a desired response while evading detection as doing such. It was actually used similarly in at least one academic paper back in the nineties: "Identity and deception in the virtual community", by Judith S. Donath.