They have to be. Basically helicopters fly low enough to be out of controlled airspace, below where airplanes should be. They’re slow and maneuverable and may want to go anywhere so control basically doesn’t care as. Long as they stay below controlled airspace. It usually works

In this case they were clearly talking to control, but the tower relied on them to see and follow. Where did that normal procedure go off track? At the surface they said they saw the jet so it’s one them, but it wont be that simple and I’m sure there will be confounding factors