@Dowjonsie - Yes, it is possible as can be seen here (I think this is what you're refering to).

This is SASHA-16 with the whole figure selected, then you go EASYPOSING>TORSO>Hip Rotate X. You will notice that unlike other figures, everything above and below the hip stays vertical while the hip is rotated, very nice! Cannot tell you how it is being achieved as I've only recently installed her and she appears to have been created by some figure wizard who can do clever things with the Poser dials, but it does at least show that it is possible, which is not surprising actually since Poser is very powerful animation-wise under the hood (it's just got an atrociously clunky animation interface).