i recorded that episode and watched it recently. after the added all the blocks she
stitched around the outside edge, leaving only enough of an opening to turn it rightside out. she poked out the corners to square them off. she closed off the opening by machine and topstitched around the edges. at the time that she was adding the blocks, she was also adding sashing with the same method. . when the whole thing was rightside out she tied off the quilt at the 4 corners of the sashing, where the blocks met the sashing, at the place where the sashing crosses.
does that answer your question? was there a question? personally, i don't see the advantage in doing it that way, but i guess she does.