Not sure if I agree. I have a hunting dog and have trained her to heel when I walk in the woods. If I let her sniff around, she catches one whiff of a deer and bounds off. It's her instinct and she does return to me as soon as she loses the scent, but she is good in chasing and has been away for half an hour at times when she was young (fortunately in fenched off private area, although I felt horrendous for the deer). I know when she does that, she is blind and deaf to all but the scent. If the deer jumped the fence and crossed the highway, she would follow without a second glance. As someone mentioned above, the moment when I can no longer keep my dog safe is definitely when I consider her out of control. It's fine if give scents chase a little, but not if she goes out of my sight and runs headfirst into dangerous situations and at that moment will not respond to recall. When she heels I have her under control. However, when we are in an area without game scents, she doesn't need to heel as she would have no reason to not listen to recall or plunge into dangerous places. Hence in those circumstances it is fine is she runs off a little distance to play around. I would still count her as being under control.