SQUEEEEE!!! Yes I am that excited about this technique and I am loving it. For some reason I had been putting off learning this. Actually turns out there is nothing to learn. It is just as easy and simple as Raglan sleeve shaping but looks so much more polished and finished. I am a lover of top down seamless knitting. I just feel that it is less of a hassle and uses knitted fabric’s attributes. Knitting can be three dimensional using increases and decreases and can be shaped to fit your body.
This method was created by SuzieM on ravelry. She has a wonderful, very helpful and amazing group there too to help you with any questions. This method has been around since 2010 and is quite popular, the group has a page listing many of the patterns that use this way of making sleeves.
You should totally check it out.