It is caused by the vibration in the driveline. It's not the amount of wheel hop that causes it, it's the frequency of the vibration. Knock detection is frequency dependant not amplitude dependant. I have seen it with wheel hop and just spinning the tires.
Thanks Mike I too have heard just stabbing the pedal at a stop light and spinning the tires can set the knock sensor off. I am looking into ways of eliminating this.
Can be a funny thing. I used to have wheel hop so bad, I swear the back end was jumping up and down 5 inches, and it felt like a jack hammer. LOL! However it didn't consistently register knock when that happened. Had to be the right frequency.
Here's an idea...stop spinning your tires. Besides, they will last longer, and spinnin' ain't winnin'.