Depends on how they are adjusted. Hardcore (bonkers) riders have them crancked up so that only a hard roatation of the foot will release them (kick out the heel).
Me, I have mine so loose that a good tug...in any direction...(even vertically) will un-clip. I do tighten then for MTB riding...a little
My pedals are set at the tightest level. And with the few off's I have had they have always unclipped.