So, my assumption was correct? (Unposted assumption only made as I was reading every comment in this thread...)
The optimal mic locations are chosen based on someone playing a guitar, through a head, through the cab to be captured, through each mic and mic pre, into the console, observed through the monitors, then adjust the mics and fader balance until it sounds the best? Or until it sounds the most like it does in the live room? (I should've left my auto correct in there... It said 'love' room. Lol!)