Every venue, small or big, room, club or hall has an ambience, unique reverb time, atmosphere, noise etc., it's never a veil of flat grey or black and controlled travel of sound, just close your eyes and hear how much there is just in your living space. The musicians were interacting with one another and playing together during there would be a lot of crossovers in any kind of space unless that's present in the recording you wouldn't have nothing like the SRX issues unless they were all in their individual anechoic booths putting tracks down here and there which AFAIK wasn't the case here. These were mono recordings to boot there should be plenty of ambience there.
david