Given the fact that Bennett, Avril and Clark have all been caught out doing it, it's clearly something that's both coached and encouraged.
We've been caught out 6 times in 189 defensive snaps (around 3% of the time), I suspect it's still 6 times more than the coaches would prefer, but that the advantage gained on the times where they get it right outweights the occasional disruption (e.g. 4 consecutive 3 and outs for the defense to start the game).
Granted, I can recall at least one third down converted by defensive offside penalty against the Titans, but had the offense managed to do something in the 4 possessions after the defense had taken the Titans off the field, maybe the defense would have been sharper in the 2nd-4th quarters - less offsides and less big gains too.