The game one strategy was to only play Hartenstein when Wemby was not on the floor, and have him only come in to match up with Luke Kornet.
Now, there was also early foul trouble that limited Hartenstein, but the strategy of targeted minutes was still in play.
The coach did change strategies for game 2, since they lost game 1, but had the same strategy been implemented, those odds aren't as far off as you think.
Coach also knew he would play Hartenstein more in game two, but did the public know? I tend to want to agree with you that , those odds seemed outsized, but there was a wierd set of circumstances there.
On another note, Hartenstein was allowed to cheat on literally every defensive possession. He just holds Wemby's arms, hooks him every time, keeps him from being able to move, nearly every possession.
Add that to the massive amount of no contact flops OKC gets it seems to me that San Antonio is better than OKC if the rules were followed.