Just a guess, but the spray takes the same flow rate and splits it up into many smaller less powerful streams. With a single jet you get adequate movement throughout the tank rather than just along where the spraybar is. I find that my aquariums had a lot of dead spots when I was using the spraybars. That's just a guess, but he probably does it because he doesn't like the way a spray bar looks or something crazy like that
. Who knows?