I don't personally think any abductor would take the risk of climbing in & out of windows, someone exiting or entering a door is an everyday occurrence, but if you see a person trying to climb in or out of windows you'd immediately take notice.
No-one climbed thru that window and neither was Madeleine passed thru it, altho Heris theory could be a possibility.
There is too much effort being made to take the eye away from the front door being used and too much effort being made to try and push the window. Just look at the Pat Brown fiasco. Having intimated the window had just Kates prints on it (NONSENSE!) they even went to the trouble and expense of cutting down a fine row of trees and fitting a huge search light to try and prove that the window and blind were part of a set up by the Mccanns. Because it was so obvious with being so overlooked, that no abductor would go in that way.
Earlier, we noticed that the lifter would have had Madeleines head on his right arm, yet bundleman had Madeleine on his left arm. Therefore it appears that there were at least two peeps involved (+ the director of ops / getaway driver, so probably 3 peeps) and she was passed from the lifter to bundleman, hence M's head moving from rightarm of lifter to Left arm of bundleman .
The window was opened for a number of reasons
1) to clear any fumes
2) to give natural light
3) As an escape route
4) To give support and advice to the lifter
5) To pass things thru to the lifter
6) To present a Red Herring that madeleine had climbed out that way, or ...
7) To take attention away from the front door, with its obvious implications that a key was used .... so there was a connection to OC itself
8) To have good visibilty of anyone approaching across the car park or along the walled pathway
Plus another couple of things which I cant remember atm