Why is the secret German spy report on the AfD party only filled with public statements?

The German domestic spy service, the Office of the Protection of the Constitution (BfV), has released a 1,100-page report on the Alternative for Germany (AfD), which it used to label the party a “confirmed” right-wing extremist party. The report is huge and reads like it was written by Antifa, but that was to be expected. […]

Source: Why is the secret German spy report on the AfD party only filled with public statements?