They should probably have a talk about that later- it's not inhuman, but it's certainly unusual for a kid to have that much pain tolerance. One interesting thing that Papyrus might notice however is that while they're certainly trying really hard to attack, they...

Don't seem to really act like anything more than hollow copies. He may be in more of the clear than he thinks! (Except not really. It's just someone else's will in there, alas,)

Leaping into where they vacated is easy- easier still due to the fact that since none of them shattered, no more are spawning.

...Yet. The four manning the shields are ever vigilant however, and those in the river are making to charge as well. It's very much become a game of flag football for this poor skeleton.