It is useless, sorry.
There is no weight for a first round pick versus a late round pick. There is no consieration for whether a player makes a team. The sample size is too small and having a pro-bowler could easily impact the decision.
Let's look at some possible scnerios.
The Cardinals have pick 210, they take a QB knowing they would like to find a third QB for the roster for camp to take the load of Murray. They take one, he doens't make the team but is put on the practice squad for six games and is cut. Then who cares?
The Eagles landed two good receivers in teh draft 6 years ago and now are paying them each $15 million. They have decided to dedicate money elsewhere so for backups they just keep using low round picks on WR and churring through them in two years and letting them go.
There are too many items that can throw this report into wacko land and dramtically increase or decrease percentages. That is what makes it usueless. It lacks any context or weight as we know first round picks are more targeted selections than a seven round guy when many teams might take an 8th or 9th guy and he has no real shot to make a roster.
And yeah I knew WR was where they invested the most when you break it down like this. Most teams will carry what 6 guys and maybe a kick returner that is usually a WR. That is what like 14 percent of the entire roster so it makes sense they spent draft capital there. It would probably be Oline, but the survey broke down T, G, C while not breaking down inside or outside WR.