So Penn State's AJ Harris, a CB, PFF says he gave up a single reception thus far in coverage, for like 35 yards.
Chat, that reception was a bubble screen, where he was isolated, and happened to be playing about 8 yards off the LOS, and the opposition pulled two lineman over to him, and had the defense leveraged, so effectively thr WR caught a screen, and the defender had two lineman blocking him
And PFF counted that as a reception/yardage against him.
This is why PFF's grades should be entirely discounted