I remember watching it and thinking that the two seemed awfully close - in the simulcam replay - for there to have been that much of a difference in their times.
There had to have been an error somewhere - either in Cooper's reported time, White's reported time, or in the simulcam replay. The most likely error, I supposed, would have been in the simulcam replay. However, having it be in Cooper's reported time might just earn him a few extra million dollars.
Whereas teams which, after the combine, may have been evaluating Cooper as being a great route runner, having great hands, having an excellent work ethic, and - due to his 40 time - being a guy with good speed who plays "faster" than his actual speed now have to turn that potential "weakness" or "caveat" in their evaluation into a strength by evaluating him as a guy who also has elite speed.