For the "long" 737 like the 800, 900 (and even the 300 maybe) the flare is sensitive and that's not easy to decrease the sink rate below 200/150 ft per minute (that should give you a standard load) with flaps at 40, but quite easy if you keep some thrust til touch down. Thing is keeping thrust during touch down is not standard procedure for many reasons, one being, for example, that the speed brake won't deploy automatically, so one method is the one you mention, it gives you thrust during touch down (the engine don't have time to come back to idle) while the thrust handle is at idle and the speed brake will deploy with a lower pitch up attitude that should prevent any bounce.
However the ones able to master this non standard technique are the ones already confortable with the standard, normal flare. Useless then at the end.