As the person who showed Dunccan this \"bug\" many moons ago, I completely agree with you.
I do not use it in combat and I didn't expect Dunccan to either.
It would be easily fixed by ensuring the jouster (and it doesn't have to be a knight) ALWAYS has to complete the full joust run even if they skewer in the first location.
I hope it is fixed, but if it isn't, it would be nice if it at least wasn't blatantly abused.
Krill
Written by my hand on the 4th of Paglost, in the year 1136.