Finny is more like himself in Chapter 11. What does he do that reminds us of the old Finny?

In Chapter Eleven, Gene arrives back at school, and finds Finny involved in a snowball fight at the edge of campus. Gene slinks away, afraid that someone will ask him how things went with Leper, but he is caught by Finny, who pegs him with a snowball. Gene finds himself caught in the snowball fight, which, at the end, has all of them pelting Finny.