O.K., first off, I will state that I was unclear on the rules. Been a while since I read them.

If a shot is not called, the opposing shooter has the option to take it or pass it back. This is what Thorsten did. No rule violation.
According to another poster, apparently in the players meeting, they agreed that they did not have to call obvious combos. That being the case, Thorsten had no choice but to pass this shot back as the ref had to call it. To do so otherwise would be very dishonorable. So, nothing against Thorsten at all, but no big deal that he passed it back. He had already agreed to do so.
My whole problem with this all, is that if one is playing by a set of rules, then they should play by that set of rules. If they don't like the rules, then play by a different set of rules. But, if in a tournament, you have a set you have to abide by. You don't go getting to change them as you go along. When you abide by the rules, then you have integrity. When you don't, you don't.
Now, as to this case, the rules state that you should call non-obvious shots, such as combos and banks. In this case, there was an agreement before the match, that if they felt it was obvious, even being a combo or bank, they would not have to call it.
If that agreement was not there, I feel there would be no loss of integrity on anyones part to take the shot after their opponent did not call it. That's part of the rules, and, especially at the pro level, you are responsible to know what rules you are playing by.
Someone else , I think Williebetmore, asked when golf would be brought up. I'll do it now. You have a golf tournament, you are required to turn in a correct score sheet, if you don't, you are disqualified. Not too long ago, in some big golf tourney, some one inadvertently turned in an incorrect score card. Their intent was to be totally honest. But, there was a wrong score on it. They were disqualified after getting well into the money.
Now, according to some on here, the rest of the golfers should have said, "no problem, we honor your score". That did not happen. The guy screwed up, and paid dearly for it. I'm sure not one other golfer thought, "hey, we know he wasn't trying to cheat, let him have the win." They knew what the rule was, and felt bad for the guy that inadvertently broke it. But, the rule stood.
So, my whole stance is, abide by the rules. In this case, Thorsten did. Both the written rules, and the rules they agreed to in the players meeting. While I feel that Thorsten is a very respectable player, I don't see where this particular call makes him an exception to others. All he did is keep his word.???