The Combine drills are used in a historical sense and are not considered exclusive to a player's success. NFL scouts, Director of Personnel and GM's know a range for each drill which produced pro players, if you fall into that range then historically, you have a much better chance for success, if you fall out of that range then they know, the likelihood for your success is much smaller.
After the drills, what they have seen is just used as a tool from which they can go back and review the film to see how you used it. It just gives them a tool by which they can more reasonably judge film. The results of the Combine drills are useless except as a tool to judge prospects on film.
If we take the bench press, it certainly doesn't tell the whole story about functional football strength, but it does tell pro scouts etc. how hard you worked in the gym to get better. It is a strong indicator of work habits not just physical strength. However, even here, there is historical evidence of the range each position should fall in for future success. Each team has a list of the historical success rates based on whether or not the prospect fell into a historical range for success or failure. It tells them the % for success if you are within the range or outside it. If group 'A' is within a positive range, say 95% and group 'B', 5%, isn't, how high is a group 'B' prospect going to get drafted, even if there is a 5% chance for success.
Just some perspective on the Combine.
And proud of it!!!