I think it's called grasping at straws, m'dear. Let me try to be clearer so you will be able to agree with me, or at least, be able to see my point.
I was contacted by the claimant's family, who had already obtained the Victorian DNA sample. I told them they should be tested. (The claimant was desceased by the time I was contacted.). I suggested they test the woman's children who were living at the time instead of exhuming the claimant. The son's mtDNA did not match that of the maternal line of Queen Victoria. IOW, we could exclude this man as being related in the maternal line to Empress Alexandra, Princess Alice, or Queen Victoria (and any of their matrilineal ancestors). The test clearly showed the claim was false. Nothing was murky, I was done.
Then (and only then), the son said, he was not his mother's natural son.
I understood what you posted before quite clearly, thank you. But my questions still are: did this claimant claim to be GD Tatiana or another GD? And: did you ask the claimant's son why, if knew that he wasn't her natural son, did he allow them to go through the testing in the first place, and only said something about it when his DNA didn't match? And the last question, which to me wasn't really clear from your post: do you believe that this person wasn't this claimant's natural son? It sort of sounded from your previous post that you may be considering this as a possibility.
1. To my knowledge, the person herself within her lifetime was never specific about this. She does, however, look amazingly like an older Tatiana.
2. Since he had never expressed any doubts about his parentage prior to the testing, I felt this new claim was not worth considering.
3. I have no way of knowing one way or another whether or not this is true or not. My conjecture is that, if a person comes to me and says, I am the grandson of the last Tsar of Russia, and he shows me pictures of a woman he says is is mother, who looks like Tatiana, then I am reasonably certain he thinks:
1. He is his mother's natural son.
2. He thinks his mother was GD Tatiana.
And, if after testing, he is shown not to be genetically related to the Romanovs, my further conjecture is that he was mistaken in claiming relationship to the IF and that his late statement about not being her natural child is grasping at straws, and not true.