I know exactly the video you are takling about i watched it and thought maybe one day i'll give it a try and when that day came i couldn't find the video anymore,this was a long while ago. I remember she made her binding as usual then with water soluble thread she sew the yarn inside the fold of the binding like pipping, took the soluble thread off the machine put regular thread and sewd the binding as usual then turned it to the back pressed and sitched in the ditch from the top the reason for the yarn she said was that she could feel the yarn with her fingers when stiching from the top and it was more even on the back thats what i remember but like i said couldn't find the video again