Thanks for this, @utkarsh.ayachit. Unfortunately, as I outlined here I am still struggling with recreating the same build with Catalyst on 5.10.x, but if you say that FetchData can sort out this problem, I will give it another go, presently.
I am just surprised that there is no other way to get a reference to VTK object. I understand ProgrammableFilter is a proxy, but we even specify vtkPolyData as output so I was looking for a clean way to get just that.