There is a lot of nuance that goes into how guitar is played which might not be obvious. Offsets for string timing, minor variations on fret-board pressure, pulling strings a bit either because of the way the chords work or for pitch reasons... it's just very complex.

Playing with a plectrum (or a thumb pick, or a bow) is very nuanced. I'm impressed that this mechanism works- it's a neat thing.

At the same time the mechanism of what fingers are doing when playing is very complex in ways that even good players and teachers might have a hard time enunciating. In addition having a good understanding of nuance in instrument, the nuances of performance, the nuances of the musical pieces, and being able to formulate what that is to a student is difficult and rare.

I'm not surprised that a smart and talented EE might not be able to know all that in addition to their more technical domain knowledge.