While I think it was the right decision, I don't think OP is crazy. It's a risk reward calculation, pure and simple. But I think it is close.
The difference between 3 and 6 points is not that high in that situation. If the Bills were out of time outs or there was only a minute left, it is different. What is the difference between 3 and 6. Well, if you stop them outside the 35, you win either way. If you give up the TD you lose either way. So, the only downside is this scenario: (1) you don't get the TD or a defensive penalty that gives you 4 more downs, (2) they get 45 but not 80 yards, (3) they make the FG. And even then, all that has happened is you reduced your chance of winning to 50/50 in OT.
There are two added benefits: you give them at least 10 extra yards to have to go even if you don't make it, and you take away their no-risk fourth down inside the 35 yard line.
On this last point, I would love to see the stats. How do teams do in the fourth quarter in drives where they know they have four downs per series? Usually, there is a disincentive not to go on fourth. Either you give up a fg try or give your opponent the ball back. When you are in the Bill's situation, there is no risk in the risk reward equation.
I think back to the 2007 super bowl. If Moss drops the TD and we only tie the game with an FG, the Giants punt on fourth down and Brady gets the ball last and OT is the worst outcome. Instead, they convert on fourth down. You want the TD of course, but putting your opponent in a no-risk 4th down situation matters.
One other thing you have to add to the math by the way: you might miss the FG. On the other side, one very small benefit of having 6 is you still get OT if they miss the extra point.