Good point. And if the aliens use digital communication (maybe with a bit of encryption and DRM on top of it
Even digital data uses a carrier wave.
The problem with this idea is that the human brain does not react well to large amounts of negative data. Eventually, the mental "squelch" of the viewer will drop to the point where they will see a pattern whether one exists or not.
I could see sending flagged data to humans, but this project is in "real-time". I think this is just a publicity gimmick.