apparently when they recorded the real drums, they just recorded the left & right channel out of the mixer direct to a stereo track so there were no multitrack recordings - not sure what they are doing these days when recording new real drums - I know other companies record them acoustically and with piezo sensors for a midi track also - just like guitars with midi pickups to give audio + midi ch11-16.
I had to convert a pearl kit over to mesh heads and piezo sensors using a roland brain for gigs where the acoustic drums where too loud.