Thank you, Thunderstone. So... the purpose of filtering out colour information to the bump and and displacement channels with that Subtract node is to prevent erroneous info from getting to the channels? Just trying to get my head around it... I can see the validity of having one image serve two purposes: less memory overhead. Your method would provide the greyscale without the overhead.

I know that BagginsBill will shudder at this, but I'm using Matmatic in a way he probably didn't quite have in mind: as an efficient means of creating simple materials (read: retrofit) with GC. Whilst applying a GC mt5 to a material with one ImageMap is a no-brainer, some content developers are using a more sophisticated shader, like Fabiana in her Noctia dress, which takes a bit more to incorporate GC.

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