All I can say, Betty, is that things change.
At one point Yarbro claimed that 6 out of 7 times the essence twin would be the same as the role. As the years progressed however and more charts were channeled, it became clear that the more experienced souls with a higher number of grand cycles were choosing ETs with different roles. This doesn't mean that all advanced souls do this, but it is an option.
Either way, having the same bleedthrough cycle after cycle would obviously get boring, so it doesn't surprise me that essence might seek some variety. Remember, all is choice.