I think the LNAB for a nonexistent or fraudulent person needs to be LNAB that one wishes the person didn't have. For instance, imagine that there was a profile for a Jake Fitz William, said to be a "natural" son of William the Conqueror.
Of course there is no such person, so a non-existent person can't be "fitz" (son of) a real person.
But if Jake Fitz William's identity is prevalent on the internet, that is how people are going to be looking for him, and one objective of the Disproven Existence Project is to identify the people who never existed and tell the truth about them. So people need to find him as "Fitz William."
The same would go for "Of Bohemia." He never existed, and he's a fraud, so he's not of Bohemia. But that's how people will look for him.
He should be disconnected from all other profiles, and the explanation you gave above should be on his profile so that people who find him will be told the truth about him.
And because's been disconnected, people will never find him by following a line of descent or ascent, because he's been de-linked. He'll only be found if people are looking for Teta of Bohemia, and then this will pop up to tell them about him.