Hello @Philw,
Thanks for your feedback.
I've been trying to reproduce this; however, I haven't had any luck so far. (see attached GIF)
I tried copying a Layered material (just the layered material) into a new empty file, and after pasting the Layered material, it also copied all used materials in the Layered one.
Also, I tried copying just the object using the Layered material, and it works as expected; I mean, it copies the object, the Layered material, and all materials used in the Layered one.
Looking forward to hearing from all of you.
Have an amazing day/evening.