First, connecting external nodes to a compound node does not seem to always work as connecting standard nodes, I mean by using the InputByInternalName method, that's why I'm often using an index, not the best method but it works.
Then, the code you are speaking of is just a way to have convenient names. It's true that the code may not be adapted to the said node, as two identically labelled Value_2 node inputs must be exposed as inputs of the compound node, but labelled differently, a situation that I have avoided during the development of PBSDF addon.

That being said, did you check the online help for Poser?
Typically when it comes to Cycles, you may start here:
https://www.posersoftware.com/documentation/13/HTML/index.htm#t=Poser_Reference_Manual%2FMaterials%2FNodes-Cycles%2FCycles_Nodes.htm

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