They don't use snicko directly but the 3rd umpire listened and heard the nick, which snicko then backed up anyway.
But to me there are at least 4 considerations
1. Umpires decision
2. Noise
3. Deviation
4. Hotspot
So if there is only one clue to him nicking it (a very light noise) with nothing else to back it up then the 3rd umpire was brave to go by the single consideration. Although according to the commentory the 3rd umpire did say that he saw some deviation as well
So do you think that there should be more evidence before overturning the on-field umpire?
It's a controversal decision I reckon but as you say Sam - in this case it was the correct decision.
They are still discussing the rights and wrongs on Sky!