Reverse grip moves the elbows closer to the torso, this changes the angle/stress on the rotator.
And you cannot do that with normal grip? Interesting. In fact, if you turn your wrist there will not be any effect after your elbow, there simply can't be because your shoulder joint is build to work regardless the position of your wrist by human anatomy. What happen there is you have to use lighter weights and that position forces you to use natural range of motion instead that crooked one you use to lift those overloaded lifts. There is no magic in the different grips.
