It doesn't hold true for Mendel, so it doesn't hold true.
Good, now you have answered the question:
Do you think Darwin was qualified to found the theory of Evolution, a man who was not a scientist but a major on theology?
Obviously your answer is "YES." Now that it is YES, you have confirmed that even religious people can make valid points about science. Since, in the context of the post, you admit that they tell the truth; there is no reason for them to (your words) "...expect they would admit to lying!"