This setting is supposed to allow/disable "no recompression required" on supported codecs (mostly .avi) when rendering.
When unchecked all frames are supposed to be rendered. This is not happening. It passes compatible frames unrendered no matter the setting - checked or unchecked.
“In order to perform rendering without recompression, the width, height, frame rate, field order, profile, level, and bit rate of the source media, project settings, and rendering template must match. Frames that have effects, compositing, or transitions applied will be rendered."