I really don't think it does David. Whilst they don't need to be specific about particular routes, the kitchen window was up there as one of the favourites. You may think it's silly, but that doesn't really mean a great deal.
Heck, there wasn't that much stuff in front of the window, it's not out of the question that he purposely placed the items there to make it appear as if obstacles were in the way. Setting the scene, just like he did in other areas (bible, Sheila, phone call).
Or he just left via another unspecified and unknown route.
Sounds like you want to 'shoehorn' JB in to a particular route.
It's a bit strange really, because if you did actually strengthen the case that he left via that window, then surely you are just reinforcing his guilt?
It is silly because it does not fit with the fundamental factors. Considering the state of Sheila's body in the crime scene photos taken around 9.30am and the autopsy notes taken in the afternoon.
-Lack of rigour mortis at 9.30am
-Lack of post mortem hypostasis at 9.30am
-Developed post mortem hypostasis by the afternoon
-Uncoagulated blood on her wounds at 9.30am
-Undigested food in her stomach
This all points to a time of death between 7.30am to 5.30am. Not to mention its also back ups the reported movement at 4am the discrepancy between the lights being on and off.
Thus he cannot possibly have entered the building, killed Sheila then exited through any window without the police noticing.
When the prosecution start ignoring the elemental areas and zero in on window latches and scratches of paint it indicates there is no substance to the case.