I didn't remember this from the first episodes. However, are you certain that the interior of the bedroom is the same in those first episodes as it is in the later ones? Perhaps Vicki's room was on the ground floor when she first arrived at Collinwood and she later moved upstairs.
Two filmed sequences shot on location at Seaview Terrace show us Vicki looking out her bedroom window, and David looking out his. Vicki's was clearly on the ground level just to the right of the front door, while David's was on the second floor, front of the house. The two rooms were nowhere near each other despite the fact that we later see their bedroom doors down the hall from one another.
Obviously these location shots were done prior to when taping of the actual series began. They were probably only allowed access to certain parts of Seaview to film, hence the exterior windows they chose to use. No doubt Dan Curtis dismissed the discrepencies of the interior sets matching these location shots.
BTW, I've never been convinced that David's room is actually the second floor of the tower. The exterior shots of his window/room never depict it as being in the tower, do they?
The shot of David looking out his bedroom window (after tampering with Roger's brakes) show his window to be at the front of the house. The tower is in the back of the house. I don't believe they ever intended for David's room to be in the tower, despite the curvature of the interior set. Nobody ever mentions any rooms in the tower except for the one and only "top" room where crazy Jenny lived.
