I always found Papyrus' death dialogue in a neutral run weird. Its like he's either being silly as a coping mechanism, or he isnt aware that he's dying.
There is also the fact that Papyrus goes out of his way all the time to make Frisk not feel bad.
He’ll call Frisk selfless when they “Insult” him, saying their doing it to make him feel better about fighting.
He’ll call Frisk humble, when “I have zero redeeming qualities” is selected, saying that they remind them of themselves.
And when called a looser he turns it back on Frisk and proceeds to comfort them with the promise of friendship.
If anything Papyrus’ lighthearted acceptance of death is another way he is trying to not have the human feel bad, like “HAha woops! didn’t see that coming!”
Papyrus is too good for us.