I used to work on those types of machines in another life. They were just coming out when I got out of that field. They are pretty slick machines. They use no pressure at all. The one I saw had a dual tube assembly that went into the fill tube and sucked it empty (engine not running) The fluid is measured by pressure differential or some even used capacitance probes. Once it sees no more liquid coming out it than refills through the other tube using a pump. Then the engine is started and it, qt for qt, matches what it is sucking out and is putting back in until it uses the amount of tranny fluid you set. Unfortunately, this method has more dilution, which is not a full exchange or "flush" as you stated. It is the fastest setup though. The newer ones can hook to cooler lines or dipstick or both I believe. That picture has cooler adapter fittings so it must have modes to hook to the cooler. Going through the cooler is much more effective in getting all the fluid out, again, with no pressure. I am a believer in full fluid exchanges. Some report that after doing some of the "flushes" they had tranny failure, so either that tranny was poorly maintained or abused or the flush machine was a power flush machine which is more likely to cause pump failure in the tranny or the machine itself was improperly operated or calibrated.