Difficulty of repulsor membranes

[Morlock]

I was planning on making some macerepulsor membranes with clearmoon jewelry mounts, as theriansim said it should be at 80 difficulty. When I went to make them, the difficulty of the membrane was not affected by the jewlery mount - it stayed at base 55 difficulty, no matter which jewelry mount I selected. Is this the intended behaviour or is it a bug?

[Lifewarden]

An item affects the craft difficulty only if it has an immutability stat listed on it. Jewelry mounts doesn't have any, (trims aswell). I thought this was reported to Aknoth already, no?