Of course , the OP probably already knows not to put his foot in so far. But, he has already lucked out once in being dragged and still here to talk about it. There may be all kind of circumstances adding to this. I applaud him for being proactive and looking for safety release stirrups. He can still work on improving his foot placement.
I know not to put my feet in too far, but from time to time, something may happen where you get "jostled" enough to lose that placement and your foot can go too deep at just the wrong time. I know this happends to me from time to time.