As neat of an effect it can't be actually getting the oscillations of the strings. For one, the distortion appears to be fairly bad in terms of the number of harmonics. But mostly it's because the wavelength is way too short. You want to vibrate the string at the fundamental frequency which will have a wavelength twice as long as the fingered string. The fundamental frequency and its harmonics will have wavelengths too long to be captured like this. The video's comments already provide the more plausible explanation. That the result is due to a rolling shutter which is creating a distorted image.