>>528595137
For one thing, once the scene goes on a little longer, Toriel asks aloud where the hell Kris is, so no, Kris is not typically gone THAT long.
With ch4 context, Toriel seems to be specifically referring to Kris having a habit of extensively washing their hands.
It matches up with Kris washing their hands after painting The Man Behind the Tree and getting the text
>between your fingers, a faint grey crease glittered stubbornly.
>...you can never wash it all away.