Z order doesn't seem to apply to dual-stick mappings

[ComplexPlane]

trafficstars

Hello,

I'm trying to create an effect where two paths are both mapped to the same stick, but one path shows at layer -1 while the other one shows at layer 1. There's a black mask at layer 0 that the layer at -1 is supposed to show through.

Sample

The paths in question have a munia:z-order attribute.