It all comes down to geometry of the sensor, flight height and overlap. With a DJI camera it might have allowed you to do that but the 6K is pretty large but has a tight field of view. This is cool but but it means you have a smaller footprint on the ground. This means that 80% has the images being spaced tighter than the camera's minimum framing rate will allow at the minimum speed so something has to move... We bump the height up accordingly. If you bump the height back down it will adjust the overlap. We are trying not to let you plan a flight with parameters that the camera can't perform for.