The interim report had very little that was unexpected, so I doubt that was the reason Dose left.
As it has publicly been stated, there were diferrences of opinion. The sub text of that, is that the board wanted control over the running of the airline, instead of letting the PCE run the airline.
It is understandable that the board would want more involvement after the way GF has spiralled downwards for the last decade.
However, it is also understandable that Dose did not expect to be just a figurehead and thought it was better to leave than work with his hands tied.
You pick your story, you pick your fight.