As I see it, the problem is that the industry standard from which the PNU is derived is in itself an abstract unit. The Object and DXF units don't refer (although I am completely ignorant here) to any real world measurement (cm, inches etc) which we would usually use to compare everyday objects or people heights etc (those things which we are emulating in our 3d scenes). 

So at some point someone decided (or perhaps didn't) that a Poser figure was going to be 'This' tall in relation to a PNU/OBJect/DXF unit. Dr Geep came up with his measures and eventually the developers of Poser and then D/S came up with theirs - problem is they all seem to be different decisions. In the meantime loads of content is made that roughly works together and nobody wants to go back and rescale all that to a new standard set of units - no, we the punters can waste our time doing that time and time again. Sigh...it wouldn't happen in a CG studio.

All this seems further complicated by the fact that other software uses different scaling etc, so bringing an object modelled in Max or Lightwave into Poser is a guessing game.
I should note here that I learned 3d with 3dsMax, which only uses real world units (well, Max 5 did anyway), so everything made and rendered within it could easily be referenced to a RW source - I measure the height of my doorframe and model it accordingly using cm or inches etc. And a figure made in the same environment to a RW height naturally looks the way it should in that doorframe. Easy. No having to judge whether something 'looks' correct to my eye before I render. Should I feel I want to make a character more imposing on a scene I can play with camera settings. Actually rescaling an object is a last resort, artistic licence decision. 

I guess I hadn't realised how messy content creation is for Poser and D/S. If nobody really cares then I suppose that's just the way it is - a collection of disperate individuals making stuff that roughly works together. I would still suggest that content creators are making stuff based on some kind of standard (e.g. does it work with V4 or G2 James etc), it's just that it's a fuzzy standard that differs between creators. 

It's no surprise at all that we sometimes get all confused about how tall figures are meant to be, or that this characters head may look too big.

Ok, I've burned myself out - maybe it's not really a big deal anyway.

 

PoserPro2014(Sr4), Win7 x64, display units set to inches.

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