If they have >5% positive difference between 2nd finishes and 3rd finishes it shows that they know how to effectively navigate the end game so that they end up with the most points possible.

Unless we are talking about tournaments, 3rd place is the last place that you want to be on the higher tables, and players with considerable experience know that and will do whatever they can to avoid 3rd. Take a look at the past leaderboards:

http://kdice.com/monthStats/44806825

Starting from the top:
Fonias
Me
Zoid (or at least I think it was zoid)
Das
Jurgen
Savif
Adcurtin
Vohaul
Etc.

All of these players I would consider above average when it comes to end-gaming. So I guess what I'm trying to say is, the key to being a better player is to never take 3rd unless you absolutely have to.