New parenting lesson for me

So I was working in my yard today as it was a beautiful sunny spring day. Well I hear a child crying for a very long time. It is a neighbor in the back yard and down about three houses. After about at least 20 minutes of this child crying, I start thinking to myself something must be wrong. I see the child standing in the same position for all this time crying loudly enough that I can hear him, and see no supervision whatsoever. Well I finally decide to go over there and make sure that he is alright. I see no parent or guardian outside and walk over to the childs fence and ask him if he is ok. He doesnt answer so I ask where him mommy is and he says she's at work. Well now I am greatly concerned as this kid is probably only 3 or 4. I go to the front door and after a huge dog bumps against the front door, I hear someone on the phone say I gotta go. She comes to the door with another child in her arms and I let her know that I am concerned about her child who has been crying loudly for sometime. She is offended that I came to her yard and says it was only 12 minutes she was timing it. She proceeds to tell me that she is trying a new parenting skill. Her Pediatrician recommened it! She told her son to take a nap and he wouldnt and proceeded to cry. So she is ignoring him rather than give him negative attention. Well I think I must have stood there with my mouth agape! I can understand new parenting skills, but I dont think leaving your kid in the backyard alone for at least 20 minutes....(it truly was closer to 30 minutes) while you're inside on the phone is a great new skill. Maybe I'm old fashioned, but I think maybe that new skill was misinterpreted by the parent or other wise that Pediatrician should have his or her license revoked.