BS penalty. Int. grounding on Jameis.

Anyone can explain to me why Winston spike the ball on 3rd down when he had 20 plus second to run a quick play?
The Saints coaches have to clear that up, as well as the clock-stopped spike. If you're spiking to kick the FG, you should leave a lot less time on the clock than 0:19, so that the Falcons can't come back (or at least force the Falcons to use a TO there).