Here’s a good example of phone camera sensor aliasing for an aircraft propellor. I am familiar with the phenomenayou are referring to because my wife and I have owned a general aviation airplane and have lived on a small airport for approximately 20 years. What we are seeing in the iPhone video is not the same thing; it is quite simply a hoax.
First, the magnitude of the movement of the strings while resonating is too great. If I am watching sound from a relatively pure source through a microphone such as the sound made by a single guitar string on my oscilloscope I can magnify the wave produced electronically. The waveform shown on the oscilloscope does not directly represent what is physically happening to the string. It also does not mean that the string is vibrating with that great of movement. Again it is a representation of the wave form of the sound not a representation of what is physically happening to the string. Additionally, the movement of the larger looser strings should be proportionally more than the tighter higher frequency strings.
I took some stills from the video and the wave form shown on the strings is an odd saw toothed shape of incredible magnitude. Do you really believe that the B string is moving that much and in that odd shape? This simply is physically impossible.
You are more than welcome to prove me wrong by placing a camera in your guitar and trying the same “experiment”. I am afraid that you will be disappointed by your results.
First, the magnitude of the movement of the strings while resonating is too great. If I am watching sound from a relatively pure source through a microphone such as the sound made by a single guitar string on my oscilloscope I can magnify the wave produced electronically. The waveform shown on the oscilloscope does not directly represent what is physically happening to the string. It also does not mean that the string is vibrating with that great of movement. Again it is a representation of the wave form of the sound not a representation of what is physically happening to the string. Additionally, the movement of the larger looser strings should be proportionally more than the tighter higher frequency strings. Here's a slow motion video from a Brazilian guitarist showing the motion of his guitar strings taken on a Moto X cell phone at 60 frames per second and then played back at 30, but shown longitudinally, along the strings, not across them so that the scan line of the shutter does not introduce artifacting to the sine wave. You will see that guitar strings do indeed have such a magnitude of motion. So much for that argument. There's another video on YouTube taken at 1000 & 2000 frames per second, but it looks as if the videographer loosened the strings because they appear floppy, but that may be an artifacting of the high frame rates.
This video shows some interesting wave artifacting on a a guitar and a violin as well.