Nested parametric cells

I'm investigating nested parametric cells and I'm curious about their usefulness based on what I am experiencing. I've created a nested parametric cell which consists of a line which has 4 nested drilled shaft parametric cells in it and constrained on the line.

When I place the parametric cell for the line I only see the variables for the that cell and not the drilled shafts.

After placement I can see the drilled shaft variables when looking at element properties, but they are greyed out and I can't change them.

Is there a way to make the variables accessible for the nested drilled shaft cells? Or is this working as designed?