I now believe it's a red herring. Put in "Irrevocable" and then watch them move on to "Abolish, void, nullify, renounce, repeal, retract, vacate, rescind, or repeal" 1.0a. Or just figure out a different attack vector.
The reason WoTC now needs to be challenged and defeated in court is because "revoking" open licenses on a whim has wider implications--there are plenty of [for example software] companies that would just LOVE to do exactly this--and not because anybody in their right mind would even consider for one second publishing anything under any open license stewarded by WoTC.