Quote - New mat on the character, 1 light AND GC on, (no change in render settings) worked much better this time...

I have to laugh at the bullshit skin shaders bit, but in seeing the difference in renders I can understand your dislike for them. Personally, and being a content creator myself, I wouldn't blame the creators, that just doesn't seem fair.

NONE of what I have researched or have discovered or what is discussed in this thread is what I would consider common Poser/art knowledge. I could go even further BB and say you have an unfair advantage in this game...

You are right: it isn't fair to blame the creators for using a kludge that worked for years to compensate for Poser's shortcomings. However, things in Poser have improved, but content creators don't really want to go from gibberish workflow which has worked for years to linear workflow which GC actually requires. So no, I'm not saying they are wrong for using it, but at the same time, as a discriminating Poser artist, you'll want to familiarise yourself with the difference and endeavour to understand how to make your materials more consistent with the application features you are currently using.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks