Yes, she had to go OVER the railing, which is why he lifted her so high. But then (when viewed from the back) he then lifts her up onto the railing.
At this point in the video, you can see how much taller Sam is compared to Chloe at his right side. He shifts her to his left side, and still appears to be holding her while she sits on the railing.
IMO, he would not have been able to stoop over the railing far enough to hold her on the window ledge. The ledge is considerably lower than the railing.
Again, this is from the back.
The side view really does not allow us to see much of the railing because of the support brackets under the railing and the support beams that reach floor to ceiling. But you can just make out the railing, behind the support beams.
These brackets blend with the window frames, giving the illusion that the frames stick out farther than they really do. Someone else previously pointed that out, and was pretty much ignored. That is not the window frames, it is support brackets beneath the railing, and support beams that reach to the ceiling that we are seeing in the side view.
It has been my belief for a while that his arms and head were not able to reach past the window frame to the outside.
The same for Chloe. I could be wrong, but it appears to me that she also was not past the outer window frame, until she fell after being pitched forward by SA's rocking motion, as seen from behind.
His explanation, in the DB interview, is that he is trying to reach farther to tap the glass. He bends forward at the waist, Chloe also bends at the waist while seated on the railing.
I only see SA's forearms resting on the railing, hanging past the railing, and do not see him holding her straight out. MOO