Agree with this. The assumption is, that the 100 page document actually has some significant defence in it. If you were to be sceptical could argue that they have no substantial defence, leaking the document would reveal this, thus, their approach is to discredit the investigation to once again make themselves out to be the victims.
Looking at the way they have approached this specific investigation from the start, they look like they have adopted this strategy early on. An aggressive and defensive tone from the off.
Considering the broader context of the whole Abu-Dhabi/ City ownership, if they lose this case it has a big impact on the initial purpose of the investment, being, to build positive PR for Abu-Dhabi (aka Sportwashing). Internally they may be accepting that they have done wrong, suspect the approach from now on will be of victims and will overplay the dicrediting of FFP and all investigations, probably taking the case to the absolute extreme, through every court in the land.
"The lady doth protest too much, methinks"