He doesn't look at every route of every game. Eight games is a usual sample size and honestly a full 16 game sample size isn't enough to draw any real conclusion in my opinion. But as I have heard Matt say on the audible or something he would rather have a life than to chart a full sample size of games.
For Parker who was dealing with two injuries didn't play in that much in the first 10 games, so maybe he could have fit all of his games from 2016 into his busy schedule. Parker only played on 468 offensive snaps last season.
2015 snap counts.
As you can see Parker didn't really get worked into the offense until the 11th game of the season. He did get more work in game 3 against Buffalo as they were being blown out. He had a total of 114 offensive snaps during the first 10 games. This is 24% of his plays. He had 8
targets during this time frame, seven of them in the Buffalo game. How useful is it to chart his routes during this time frame?
Parker was a rookie.
His coaches got fired.
If you watch his college games that adds more to the overall evaluation of the player. I have done that several times. Sounds like you have also 80's as you liked him a lot going into the NFL draft.
Parker certainly needs to work on his route running, that was a legit criticism of his skill set as a college player also. Many people talked about him not getting as much separation on his routes as they would like, yet Parker would win anyways because of ability to win with the ball in the air.. He demonstrates the skill and ability to improve as a route runner over time. He is not an incompetent route runner, he just hasn't refined his technique yet. He has a very quick release off the line with a variety of moves to beat defenders at the start of his routes. This is more evident in his college games than the pros where corners are playing much better technique across the board. Parker saw some things from defenders he likely didn't see as much in college. There is an adjustment period.
Parker due to his great leaping ability and body control can win contested catches frequently. So it doesn't matter as much with him to get full separation. He is still open.
If the focus is solely on route running you are kind of seeing the forest instead of the tree that Parker is. Route running is not the end all be all of a WR skill set. It is important, see Cordarralle Patterson, but it isn't everything. WR win in more ways than by running good routes.
I like Harmons work, don't get me wrong. I'm just saying you should think for yourself and don't let any one perspective dominate your view of the entire picture.