It has a seam above the bust line. The upper chest piece then is sewn down for the first 1/3rd, then has a twist and then is sewn for the next third.
I thought it gave a nice interesting look without being a low cut as many of the tops which twist at the bust are.
I might experiment on knit scraps. I wonder if it is just a round neck top with a seam and then a twist added.
I would love to hear about any patterns which use this or indeed pictures of online RTW versions
(I saw it on a person on TV so can't examine the garment close up).