Challenge
You make it sound like no trader can ever out run or out maneuver a combat ship. This is simply not true. Not, at least, according to some of the streamers I've watched and comments I've read here and among other places. Engineered bits, Sensor signature reduction, as well as a pilot's skill in evasive maneuvers all play a part.
And they really only have to do it long enough to enable a re-engagement of the FSD.
I am not sure what streamers are you watching nor I care. In my book surviving few seconds to high wake does not count for outrunning and outmaneuvering. If you do not submit to interdiction you are doomed.
Most of the trade ships are like sitting ducks for a proper combat ship and then they can only survive if utilizing max speed and boost intervals with high shield , armor and module protection...
It doesn't matter if you jettison your cargo or not.