By "UFO interceptors" you mean "hunter-killers" or just any UFO?
If hunter-killers then no, they go automatically into aggressive mode.
Also, 8 km was chosen as a minimum distance deliberately... otherwise the dogfight graphics look weird.
The fact that you can go below 8 km in standard (and also cautious) attack is a bug... a bug that nobody noticed, because no one has set such a short weapon range yet I assume.