Is the tournament leading to some consensus on how good/bad Carlsen's decision was?
Not quite. As others have pointed out, Carlsen's decision was based on factors outside that one game. With a stronger position and a large time advantage, Carlsen most likely could have won game 12, but Caruana had just tied Carlsen in 11 consecutive games, several of which had each player blunder away a significant advantage. Caruana showed he could go toe-to-toe with our Norwegian champion, and so attacking his position would not come without risks.
Meanwhile, a draw effectively changed the championship to a 4-game Rapid tournament (then Blitz if that ended in a tie), where Carlsen is a heavy favorite. While Carlsen and Caruana are roughly equal in standard chess (2835 and 2832 respectively), Carlsen is much stronger at Rapid (2880 and 2789) and Blitz (2939 and 2767). Why extend a game in an even format when a draw moves to a format you're stronger in?
Having said that, the Chess community was not happy at all to see that draw offered (source: I was unhappy). I'll concede it was a technically correct decision, but as someone who had been waiting 11 games for a win, seeing one materialize then simply vanish was frustrating. It left a lot of people asking "What would have happened if Carlsen hadn't offered that draw? How would the game have ended?", and that's the question these games are answering.
In other words, the tournament isn't leading to some consensus on how good/bad Carlsen's decision was. It's leading to some consensus on how good/bad Carlsen's position was.
All in all, the tournament showed that Carlsen had a very good position. After 56 games, black finished with 27 wins, white finished with 3 wins, and there were 26 draws. That's a tremendous advantage. Any grandmaster would be ecstatic to hear that, for a chess engine, their position was only losing in 5% of games played.
What's more, this tournament had given both sides equal time. That's not completely accurate, as Carlsen had a significant lead on time (though I've forgotten just how much). That implies these results are even too conservative, and that Carlsen may have had a larger lead.
Having said that, humans and computers play in very different styles. Because it's winning for a computer doesn't guarantee it's winning for Carlsen (though he's practically a computer anyway), but it does show he had a strong opportunity to win it all in game 12.