As the name implied, even if Lin Yun won, whether those greenskins survived would come down to how many of them died fighting the High Elf army.
Whether they could escape was another matter. Greenskins rarely retreated easily.
As for why Tyrion had proposed this champion's duel, part of the reason was that he hadn't been paying much attention to his surroundings during the battle.
But the Herald of Death's appearance had been hard to ignore. Aside from fighting the Dead Fairy, Tyrion had paid the most attention to the Herald of Death.
Yet Lin Yun had appeared beside the Herald of Death like a ghost and launched an attack.
Tyrion didn't know whether Lin Yun had used an exceptionally powerful stealth spell, teleported through space, or simply moved so fast that he'd reached the Herald of Death in an instant.
But he could say this with certainty: if that was the case, he had no way to intercept Lin Yun.
Which meant Lin Yun could slaughter his way through the High Elf army.
Even if Lin Yun did nothing else, killing all the High Elf mages would be a serious problem.
So Tyrion's insistence on a champion's duel was mainly because, whether or not they intended to kill Lin Yun, the best way to deal with him was to tie him down in a direct fight.
Besides, although the outcome now seemed all but decided, the Chaos army was still fighting desperately. They had all seen the Herald of Death die, but these greenskins clearly had no interest in taking prisoners. The Chaos forces had no choice but to struggle to the bitter end.
Tyrion hoped to use this opportunity to further weaken the greenskins' fighting strength.
Of course, there was one last reason... He really did want to