"Pinkerton" is just emf's brand of birdshead, at the time the original rule was written emf was the only one selling birdshead SAA's. Since then other co's have marketed them under different names but "Pinkerton" has kind of stuck with us as a descriptive term, sort of how all locking pliers are called vise-grips.
The Ruger Bisley failed muster on two fronts (1) It is
NOT a reasonably close copy of the gun it's named after, even the manufacturer doesn't make that claim, (2) it
IS a perfect copy of a gun created in 1926 by Elmer Keith.
I've seen Trap's home filed grips, they certainly wouldn't be mistaken for any type of factory configuration.
It's not a subject that's had much formal discussion...I suppose there should be at least some sort of basic guideline for home gunsmithing. Maybe you should post a picture of them over on TFS, Joss was lamenting the recent drought of arguing
...well, something like that.