Do you notice that MANY windows are open in your picture of the building? So the picture Q posted is only significant that someone CHOSE to open the window and that there is residual material around the window.
High rise structures in China all have two things:
1. Windows that open. Many rooms/floors are unoccupied, and they open the windows for ventilation rather than waste forced air.
2. If taller than 6 stories, the building MUST HAVE blast doors to seal the underground floors. Yes, BLAST DOORS. Watertight, air tight. Civil defense is a way of life there.
That’s an interesting point; however Q drew attention to the feathering effect seen around the window in question which most participants seem to think is residue from some kind of explosive device. I have not looked, but I would be surprised if the other open windows show that effect.