Oh, and thank you for pointing out that those two:
Reflect_Lite_Mult
Reflect_Kd_Mult
were turned on. I remember reading discussion on this topic before, and had I realized they were turned on would have turned them off. Who knows what that would have done to the look of that material, though. So, I do a screen cap and then, turn stuff off and recreate a shader from scratch to reporduce the desired effect, except using the correct nodes and setting this time.

Right.

My approach to shaders is invariably: are they valid to begin with? I've had too many discussions with people mucking around in the material room to be convinced that shaders are always developed with a clear knowledge of what exactly is going on. People go after an effect. If the preview looks something like what they're after, they'll use whatever settings and nodes and whatever to achieve that effect. Some may even test that shader in a few different lights to make sure they sorta get a similar effect in other light conditions.

So, what do I do? Try to bring that shader back to some semblance of reality? Try to reproduce the effect but correctly, with a working knowledge of what nodes should be used to create that effect? Certainly, the latter, but implied here is that I possess a greater knowledge of shaders than most developers.

In which case, I'd better get crackin'... got heaps to learn!!

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