so according to your guy's theory, the instrument that somebody is playing determines their sound?
Nope. More like the instrument that is being played and the way you percieve music itself determines what you specifically pick out and concentrate on in a song. You can concentrate on any instrument though but if you don't understand how said instrument is being played then you're not likely to be able to decipher whose particular energy or style you're hearing and drums are just drums unless you listen intently.
I'm not saying you have to know how to play either you just have to have a basic understanding (I am hearing a symbol, snare, double bass or this chord or this string, ie) I don't know guitar very well but I can pick out pitches that I'm hearing and can kind of imagine how its being played, if I had a better understanding though I'd def enjoy and get the music alot more.
Of course I could be completely full of shit but thats just my opinion