He did not. He gave no criteria for determing how "by the WR" stats are even recorded. Furthermore, Fahey is clearly using his own version of the "eye test" to make his determinants. It's not like he has hard numbers. He's making his own interpretation by watching the plays, the same as me.
The YAC average for the Bills in 2015 was 31st. It was 30th in 2016. Unless our WR's got better in 2016, I'd say Fahey is full of it.