Ok, the scope was zeroed for what range ? so if the shot was taken from a closer range than the zero range, then maybe it’s not that implausible as I thought that the frame of the window could be accidentally hit.
This might be an opportunity for Mr.Collins’s to do another experiment like his presentation of the snipers nest box which proved (seems to me at least) that a 6th floor TSBD shooter at the SE window, sitting on a box was a good position to both hide from LOS of the Hughes film and yet able to quickly lean forward and place rifle on the box on the window ledge once the JFK limo turned down Elm st.