My SIL has done this method for sometime now ... even allowing for her son to cry & scream for up to 30mins ... Too be honest i have never seen it work as her son ends up hysterical & with short of breath ... and then shes goes in to get him & she starts the same procedure all over again

Maybe she continues to use this method as 'maybe' ?? it's worked for her at some point ??

I personally couldn't witness my DD get so emotionally & physically stressed ... When she was a baby i would chose to cuddle her if she was crying until she slept (but then that's just me & that's my choice ... and not to mention she had painful colic pains )