> ... this algorithm replaces the data with a random value that has no relation to the original.
Based on that sentence, I assume that when you write "the data" you mean "the part of a picture corresponding to a person's face." But removing the face from a picture doesn't necessarily make it particularly difficult to identify the subject if the subject is very familiar to you. It doesn't matter if you've never seen that specific picture, or if you have no additional context like place and time.
Just look at the examples on the GitHub page for proof! The picture of Obama and Trump is clearly recognizable, and at least one of the other Obama photos is easy to recognize. The soccer players are identifiable from their jersies (Messi is #10 on Barcelona). Jennifer Lawrence was also easy for me to spot.