If you look at some of the monitors, same species different localities, in my opinion this is caused by inbreeding.
Some species are isolated and small numbered. Thei inbreed and they are still around and don't have the problems we might think they would.
But then again, I have heard of snake being born with one eye due to inbreeding (in my opinion it's more of incubation temps) but who knows
Until there are studies that prove the pros and con's on it, I can't say it is ok and that it isn't.