Well sure but at that point the only way for them to die is to either go in with just their escort instead of joining up with their own army, or to lose the battle. Since the chances of a leader of that quality inserted in an elite unit dying in a battle that was won are minuscule.
Duels are a thing and I am pretty sure no Grail Knight would refuse one even when it is common sense to do so... hey look another way in which they are like Chaos Champions. Are we sure the four did not have a sister they teased too much at one point?
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