Quote - The reason I asked is I am still confused as to how vendors put them in the "Pose" library for their clothing textures.

Unless you're mistakenly trying to support D|S (in which case you should really make native D|S materials) or P4/PP (for which you're limited to very basic settings as they don't support nodes) you should keep MT5s (single materials) and MC6s (material collections). There is no reason to bother moving such files to the Pose library, people are now used to looking in the Material library for these (especially with the improvements in the library for P8 and above).

Save yourself some work and stop perpetuating the concept of material settings as poses (they have their own place to live since P5).