Why would they have this in the actual PDF?

"Finally, Pied Piper has recently claimed to employ ML techniques in its Middle-Out algorithm (Judge et al., 2016), although their nature is shrouded in mystery"

This is promotion, they are getting a fake paper to permeate throughout the internet. If I had to guess, I would say they are making a statement about reproducing results in academia and not taking a single paper as gospel. If so, I think they are making their point pretty well.