There are right and wrong answers to questions.
The realist approach, like cladistics and particle physics, believes that there ultimately is a single right (ie, true) answer to our questions. If this belief is right, ie, if there indeed ultimately is a single right answer, then there must also ultimately be a single wrong (ie, false) answer.
However, in practice we have to find out whether an answer is right or wrong, meaning that the answer to the question of whether a hypothetical ultimate wrong answer is right or wrong is right if it is right (ie, if the answer indeed is the ultimate wrong answer) and wrong if it isn’t. It means that the realist approach becomes wrong in the moment it becomes right, since there then are two (orthogonal) right answers to questions.
This property is the hallmark of an orthogonal inconsistency like realism (ie, a paradoxical contradiction) – it is wrong if it is right.