Little of the topic & not that the 40 & splits dictates being drafted. The hand held times are the standard for the scouts & GM's. There is a reason everyone in the building has a stop watch except the janitors. Propects aren't invited, some invited don't run. "Apples to Apples". The combine is a showcase that many athletes spend hundreds of hours pre-combine at training complexes learning how to come out of a sprinter stance & how to stay low & forward early. It has been discussed & documented how training as a track athlete could cut a tenth or more off your timed speed. And a footbal player uses that in his game about.......Zero times. Game speed is what matters and you could see it in tape. Even at the NFL level...The 10-15 pounds of equipment is a factor along with "resistance" factors of thigh, knee, girdle, knee braces, etc. That is why they are called the "underwear" olympics. Trust your eyes in the game and you will be fine.
As far as Sinkfield, watch his highlights and you see a WR with skills. You see him throttling down because he knows the QB(s) can't get the ball down the field. The good thing you see is his ability to come back and fight for the ball. You also see a hands catcher with very good body control. You wanted to see him in a foot race for YAC but his QB never put him in that situation. He played with a running QB his first two years and a freshamn QB his last year. All of that said, He played at Northern Iowa. Level of competition a concern. He didn't play in any All Star games to put his talents up against better competition. He didn't have eye popping stats. Stats could be attributed to the QB as seen on the highlights. This doesn't make him a great prospect. His pro-day puts him on the radar. He is still an UDFA or 7th rounder. As far as speed....He has the speed in shorts. You can look for yourself below & time it if you like. Two of his runs. He is a ligitimate 4.3 guy. I came up with some 4.2's several times on his second. 10 Splits in the 1.4.