Phase noise simulation of PFD

I tried doing the phase noise simulation of a PFD using Pnoise analysis. I set the two inputs to the PFD (reference and feedback) at some phase offset and tried to find the phase noise for the output signal (defined as up-down). I observed that the simulated output phase noise varies inversely to the phase offset between two inputs. This is not expected as explained in http://www.designers-guide.org/analysis/PLLnoise+jitter.pdf . Please clear my doubt.