Moiraine

Why does it matter what their straight line speed/acceleration is when they're wearing street clothes? What if some are worse than others while encumbered with pads?

Because it establishes a baseline. What good would the data do for comparison when playings could be wearing different weight equipment? 

They should be wearing what they'd wear while playing football in the NFL, since they are being drafted to play football in the NFL (same goes for any other level). A 40 time in street clothes is not a good baseline, since different people could be more affected by wearing pads than others. It's a variable that's not being accounted for. Maybe they should test both.

Maybe Person B is faster than person A, but A is more comfortable and barely affected by wearing pads, and B is much more affected by the pads. Their speeds/acceleration while wearing street clothes don't matter if they don't translate to how fast they'll be while wearing what they wear in games. The same concepts apply to agility tests.