the details are now foggy, but i thought it had more to do with the fact that the ravens held on to their last time-out. instead of burning it after 1st down, they waited until the pats burned their 3rd, forcing the kick. i don't recall them kneeling too soon. they have a team of people calculating that stuff. pretty sure that if they could have killed the clock, they would have.
The sequence of plays.. when they took over the ball there was a time out due to change of possession.
New England Patriots at 01:39
1-10-NE 20(1:39) 12-T.Brady kneels to NE 18 for -2 yards.
2-12-NE 18( .57) 12-T.Brady kneels to NE 16 for -2 yards.
3-14-NE 16( .15) 12-T.Brady kneels to NE 15 for -1 yards.
I guess they didn't want to risk a fumble, but running a legitimate play would kill more clock. And they might have even picked up a first down. But I suppose running plays weren't part of the gameplan at all.