The danger of the pro or promaster 2bar bounce pass off the defender's back wall, as Billy described, is compounded by the fact that if its successful enough, the defender has to think of taking the 2bar off the nearest center lane area to grab or stop a backwall bounce from leaving the area. This destroys the basic principle of completely shutting down the nearest center lane (53-52 in a pull side, 54-53 in a push side) as described in the basic Center Zone D. As you can observe Rico's and Billy's and Tommy's combo lefthand grip on the defending Gbar & 2bar, once the defender has to start moving the 2bar independently in D more and more, the center holes open up, just as Billy described.
At the highest level of world class play, I can see where losing the Tornado's G3 and G1 figures will really make a difference. Almost all top singles players know and live & die by center zone D, because at their level, having only one figure, either the goalplayer or 2bar, blocking that center lane is suicidal. This also highlights the difference of the defensive game with the wider Tornado and multi-table goals versus the obsolete "long & short" D, back when you could fork both center lanes with the goalplayer and 2bar. The narrower old goals prevented long sprays and cutbacks through the lane. This is in contrast to today, where having only one figure in the back defending that lane is impossible against any decent semipro or better 2bar shooter.
I don't know if the bounce off the back wall from the 5bar is anywhere near as effective, except for showboating, because if your 5bar can consistently get through, then you can just as easily practice catching on the 3bar directly without adding the potential of a snag by the defender, which is part of good defensive play, being ready to snag misdirected or blocked 5bar passes. Although I will add that having only the 2bar figures available to snag a backwall bounce must help the percentages.
I've noted that the 2bar bounce off the backwall seems easier to control on the 3bar. It gives oneself more time to catch on the 3bar, and is easier to get through, probably because the defending 5bar is not going nuts trying to shut down a 5bar pass, while also having to concentrate on the defending 3bar, all at the same time. A "spanning" defender on a single goalplayer table, who defends with the right hand on the 3bar, left hand on the Gbar, definitely is a sucker for the bounce off the back wall. Those defenders would have to switch the left hand on the 2bar to defend bounce passes. And completed 3bar passes are so much more overwhelming nowadays, because the common snake or rollover shots on tour are so good, so machinelike, and so energy-conserving, that its even more disheartening for a defender to give up so many 3bar attempts.