Objects at different z heights, bottom layers disreguarded

Hey folks,

Am I misunderstanding something or is this a bug?

I want to print multiple copies of an identical .stl on top of each other, each separated by a thin spacer of PLA support. Each copy has 2 perimeters, 3 bottom, and 3 top layers with ZERO infill.

My workflow:

Select All, right click, select Assemble, then select Move and adjust Z of each and center each.

Everything aligns properly.

I confirmed that the parameters of each object specify 3 top and bottom layers with 0 infill

When I preview, I see that only the bottom most and top most layers of the assembly have 3 layers.
The top and bottom layers of the objects in between are ignored as if the entire assembly is treated as a single object.

I have tested this with an Assembly of two Primitive Cubes stacked on top of each other, 3 top and bottom layers each and the in-between top and bottom layers are absent.

Any suggestions?

Thanks,
Stu