I think it was clumsily designed in a way that wasn't intended but had the potential for misinterpretation (and also deliberate misrepresentation).
I was not familiar with the Governor Hub training site as the school where I'm a Governor doesn't use it, but I had a look at their website and read the statement that they had put out in response to the telegraph article.
The scenario that was provided in the example was not given in the context of training governors on how to respond to allegations of sexual abuse or grooming or exploitation etc, which was covered in a completely separate section or perhaps in a different training session altogether. The focus of that section certainly didn't have anything to do with how schools or governors should respond to such concerns.
What it was intended to do was to help illustrate the difference between misinformation, disinformation and conspiracy theories, and participants were supposed to identify which of those three categories applied to a series of different scenarios. With regard to the question that has been scrutinised, the scenario stated that the teacher "knew" the rumours to be false but was aware that the children were circulating them to help keep each other safe. Participants were supposed to select "misinformation" because the information was known to be false but was not being circulated for malicious reasons.
The issue that I have with the choice of scenario is that I can't think of a situation in which a teacher could confidently know that a rumour is without foundation without this being properly investigated, and so I consider the premise of the question to be flawed. However, I don't think it's at all accurate to suggest that governors were being taught to treat alleged abuse by particular groups as disinformation, as that very clearly wasn't the case.