The net curtains being light would not take too much breeze to make them woosh. For a long time it hasn't been appreciated that there were net curtains involved. This has been the result of the photo on file where no net curtains are visible at all.
Would the police photographer have pushed the net curtains so that the state of the window and shutters are visible?
I assume that when the family arrived the shutters and curtains were open. The nets were probably closed for privacy. They closed the shutters and curtains and the closed curtains flew up on 3rd. Kate is quite clear in her book.
I very much doubt that the police photographer moved anything. His job was to record the scene as the police found it, not to rearrange it. If the curtains and nets were opened it wasn't by him imo.
On our arrival we had lowered the blind-style shutters on the outside of the windows, which were controlled from
the inside, and closed the curtains. We left them that way all week.....
As I ran back into the children’s room the closed curtains flew up in a gust of wind. My heart lurched as I saw now that, behind them, the window was wide open and the shutters on the outside raised all the way up. [Madeleine]