Take Florida corner Kaiir Elam for instance. Elam supposedly ran a 4.47 (1st run), 4.54 (2nd run), and yet his official time was a 4.39?
Typically the 40 times are fairly consistent with the second one being a tad slower. You have to remember the 40 is a full exertion exercise, so sometimes players hurt or push themselves on the first one.
The kids all want to run the 40s. We used to do it every spring. It was always fun because one, it a lesson in reality for a lot of these kids ("No way I run a 4.9 coach") and two, it was fun as coaches to see which of our peers were either too generous or too stingy with their trigger fingers. Once the kids figure it out, you would see them all getting in line for the umm, more generous coaches. I took pride in being the consistent guy. One of the greatest compliments I have had a peer says was " Coach Daniels is a
bad word but he's never going to lie to a player. If you're slow, he's going to tell you just how slow you are." Anyway, we realized that too many of our players were hurting themselves. We'd come out of spring ball with too many pulled or injured hamstrings, or even worse, achilles injuries. We stopped running the 40 the last several years.
Back to your point, this year's Combine was the first one I can recall where the offical times were faster than the initial, live times.