There's no correlation between these 40 or cone times, with who is actually good at football .... there is an over emphasis on the wrong data. It's akin to going after QBs who can throw a 70 yard pass (who cares).
There's a correlation between measurables and who is good/great at football, but having good/great measurables does not ensure one is good at football. I would argue that
bad measurables almost always guarantees a player won't be able to play at an NFL level. There are a few outliers, but when you delve deep into their backstories you find there were extenuating circumstances as to why they didn't perform at their peak... injuries etc.
Profootballreference and nflcombineresults used to post combine results on a spreadsheet, one could toggle for the best/worst scores among all the major measurables in descending or ascending order. When one did this the top (best scores) were a who's who of All Pro's/Pro Bowlers and top players... when you toggled or scrolled down the bottom you found the busts, the nobodies and failures.
The reason the draft is a crapshoot is the human condition. Chad Jackson had amazing measurables, he had a flawless combine performance, he had good production in college... when he became a pro he let it all go to his head and became a screwup, lazy, unfocused and eventually injured.
You can't measure or quantify
"desire" or
"football smarts." Some players no matter how talented are just satisfied getting that one pro contract. After four years of highschool and college some of their bodies are being held together by duct tape and a desire for one contract or to say they
“made it.” But at the end of the day if a player has the intangibles their ability to run a 4.2 forty, jump 40 inches in the air, to change direction with amazing cone/shuttle times is what makes them amazing players rather than average players... the god given stuff.