1. Set the project settings to a 1280x720 resolution,
   insert such a clip in the timeline

2. Open the render dialog.

3. In the video tab, set the scale to 50 instead of 100 (%).
   While you're at it, also change the framerate override,
   and change the channels/rate overrides in the audio tab too.

4. Render


Result: the rendered file is always 1280x720 @ 24 fps and 48 000 hz audio. Therefore the resolution scale, framerate and sampling rate overrides set in the render dialog have been completely ignored.