While this makes achieving pinch harmonics easier, I feel that this adds unnecessary complexity to the technique which distracts from and makes more difficult the process. I stopped using it many years ago. The 'glancing thumb' works with fewer complexities but just requires more practice to 'perfect'. As I wrote in another thread, glancing the thumb is more a matter of slight changes in picking attack than concentrating on getting the thumb to glance the string (as the slight changes naturally do that for you). In most ways I hate to say it: you'll know it when you 'see' it - then you'll be able to use it almost unrestricted.
this is true, it's defnitely more work to flip the pick sideways in your hand, but once it is sideways, you will hit the pinch harmonics infinitely more easily than if the pick is held the normal way.
at the very least, it's helpful to practice "sideways" until you get the hang of how it's supposed to work, then you can focus on learning to do it with the pick the normal way