The one thing we have no info on is tag time. Just how long does it take a fielder to catch a ball head high and get his glove to the base. Or shoulder high, or waist high. What about a ball to the left or right.
Whatever the time is, it should be added on to a catchers pop time, as the race is to the bag, not the fielders glove.
From what I have seen, the true test of a catchers ability to throw out runners is determined late in close games.
If it's the 9th inning in a tie game and the other team gets a runner on first, this is the moment the catcher needs to be fast and accurate. This is the time that pitchers focus more on holding runners close so stolen bases late in a game are usually on the catcher. Inaccurate catchers with a big tag time added onto their pop time will be exposed when these situations come up during the season.