I am no expert on the subject, but I know that genetically there is more than one type. There seams to be a simple recessive, dominant, and a compilation in some. I have found it in literature, but I have no practical experience with it. I have only dealt with it in one strain.I had stubs show up in my birds several years ago. What I did was pluck them all and mark the birds. I gave them a few weeks and checked again. The ones that had grown them back got a one way ticket to the freezer. The ones that did not grow back were used.
I haven't seen stubs since then. I haven't checked super close though so maybe its time to do an inspection.
I did find a few on the shanks in the Catalanas last year. Not enough to get worked up over, and I culled the few I saw. They were also from a single pairing, which I chose not to use again. I also did not keep any of their offspring.