I may be wrong, but skills like that which have a great bearing on the selection process are like any other stat for a player. They only get the player on the radar. When push comes to shove and the final selection depends on that particular stat, it will be tested by the interested team however they test such things. IOW, if the pop time is all that separates two catchers, both will be timed by the same guy in the same manner, so worrying about a few hundredths of a second prior to that isn’t something that’s worth a lot of time and angst. 
