If you know the tuning and scale length of the guitar, you can map the note played (audio) to string and fret position without trying to work that out from video?

I imagine audio waveform is a magnitude easier than video recognition.

Video would be a pain because you would probably need to synchronise hand fretting position with picking/strumming timing to know which video frame actually 'struck' each string or chord, right?

Imagine finger style guitar or flamenco, the picking patterns are at least as complex as the fretted hand position.