Yes, you got it!

Except one thing you wrote is not right:-

The PoserSurface Diffuse_Color channel does not do everything. It only does one thing: it implements a particular type of Diffuse node (I forget which diffuse lighting model it uses). Anything else you need - such as specular reflections, true reflections, ambient occlusion, transparency, translucence, refraction, etc. - has to be implemented separately.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)