i guess my thought is that even if they managed to bat for 2 whole days and scored say 400 runs (not looking to score quickly and trying to save the game), that would give us 20 something overs to score 150ish quick runs. I know the fielding restrictions and tighter wide rules make a difference, as well as a pitch that has deteriorated, but there is still a chance we can win, and very very little chance we can lose.
Edit: Don't mean to come across to negative here, we are still in a VERY good position, and a reasonably quick(but not recklessly so) 150 runs tomorrow morning puts us in with a good chance of winning. I do however think in this case, and in most cases, especially when having bowled for less than 100 overs, enforcing the following on is the right call.