It is possible to design systems that fail in predictable ways (tear-strips on consumer packaging are an example of this) but airplanes aren't designed that way. It just doesn't matter how the plane fails when it reaches its structural limits, so no design effort is put into this. So no, it is not at all surprising that the energy dissipated in unexpected ways. That's one of the reasons they ran the last test past 100% so they could find out how it would fail because no one knew.