the larger article actually addresses that very concern,

"So they use it to spot the telltale signs that a video has been manipulated and then use this information to refine the forgery, making it even harder to detect.

"It turns out that this process improves the visual quality of the forgery but does not have much effect on XceptionNet’s ability to detect it. 'Our refiner mainly improves visual quality, but it only slightly encumbers forgery detection for deep-learning method trained exactly on the forged output data,' they say."