Never had need to merge skin presets, so i never noticed.
So it works as normal load...that's a bummer (if you wanna use skin preset for decal only).
If you only need to load decals, did you try Decal Maker plugin? You can also layer them
(off topic/unrelated to this issue)
There are triggers, if you need to load & remove decals on the fly (or any skin texture for that matter).
Person -> textures -> faceDecalUrl (or xxxxDiffuseUrl, xxxxSpecularUrl, xxxxGlossUrl, xxxxNormalUrl)
type path to load (or leave empty to remove), example:
(local) Custom/Atom/Person/Textures/decal.png or (from .var) creator.packageName.version:/Custom/Atom/Person/Textures/etc/etc.png