(Way late response, buuut)

PFF actually did an article on “tracking” https://www.profootballfocus.com/blog/2014/06/10/the-art-of-tracking-and-the-nfls-best-cornerbacks/ (although sadly it didn’t list snaps). There was also another article (that sadly I can’t find, even just trying to google relevant keywords), that listed the numbers of games the CB was asked (for most of the game), to track a WR, and the % of snaps they were across from a #1WR (however that distinction was made). From what I remember, Revis, Patrick Peterson, & Joe Haden are the only players who do it a noticeable amount (and only Revis was actually good at it, the others only at LCB).

I agree with the superiority of the signature stats, if only as the methodology is different. Their standard stats are based on each game. Then their seasonal scores are the sums of each game. Thus if you miss a few games, you are at a disadvantage to others who played more games.

Their signature stats are seasonal stats from the beginning.