Apparently the mechanism to defend the pants against stains is that extremely small "nano-whiskers" are used to cover the threads, and these block liquids from getting in and staining them. I assume the production of nanofibers is not easy. Anything that uses nanofibers can thus reasonably claim to be using "nanotechnology," just as anything using chemicals can claim to be using "chemistry." As in, "better living through chemistry," a slogan that applies to a lot of things. Why should "nanotechnology" refer specifically and solely to nanorobots?
It doesn't. Except to Jenny Everett who is a graduate of the Humpty Dumpty School of Journalism
nanotechnology
/nan'-oh-tek-no"l*-jee/ Any fabrication technology in which objects are designed and built by the specification and placement of individual atoms or molecules or where at least one dimension is on a scale of nanometers.