It's the V3 and M3 skeletons I have at present, and these are based on the fully articulated spine model.
I guess from what I've seen it's either a poser limitation or an oversight on DAzs part rather than a fault with the skeleton model itself- perhaps putting a morph control for the various movements which require scapular and clavicular movements would have been a good idea.

As I'm new to the fancier parts of Poser I won't be doing it myself any time soon!

Edit.... with regards to the posing of the skeleton within M3 or V3 (Well V4) anyone who's tried it will tell you how much fun this can be - bones getting lazy and being left behind (the radius is the biggest problem for me) if you don't do things in a certain order can certainly produce some funny results.

I've seen a few posts about problems getting the skeletons to conform, and have worked around a lot of the problems.  I'd guess that the radius problem stems from the fact that the model is rigged from the wrong direction as far as the radius is concerned. 
It must be difficult getting this sort of thing to work seamlessly, but the radius should be viewed as pointing in the wrong direction as far as the rest of the arm is concerned - it pivots around the ulna at the distal (hand) end, but the rotation of the forearm is controlled from the same place as flexion in the parameter dials - we can't have eveyrthing I guess!