I don't think that its the end of game that would be effected defensively. If someone has 2 fouls at 12 min in the first, they might be a little softer for fear of the foul call. In the last 2 minutes the value of the stop becomes more critical in a close game and I don't see players worried about fouls as much. Would love to have defensive efficency numbers when there is foul trouble to see if they show that.
I could see points being "worth more" down the stretch from the stand point of: If you hit a 3 to go up 3 with 28 minutes left in the game, they have 28 minutes to make up that 3 points. If you hit that 3 to go up 3 with 8 seconds left, they have basically one play to make up those points. Though I could just be inferring the 3 pt lead is worth more, which is obvious. Regardless of when the points came, a 3 pt lead with 8 seconds left is the same.