The pcurve is a specific type of parametric curve, but the methodology used for the pcurve can be extended to other kinds of parametric curves, e.g. a tapered one. It needs a tutorial in the near future.
As for the “Ah, in addition” part:
GDS layer (1111, 0) is a “dump-layer”. If you use an unknown layer in Nazca, your output will be redirected to the dump-layer to show you some layer definition needs fixing.