Using createSlice() with Async Action Creators Instructions

In the introduction to the Using createSlice() with Async Action Creators Instructions lesson, there is this code example:

const fetchUserById = createAsyncThunk(
  'users/fetchUserById', // action type
  async (userId, thunkAPI) => { // payload creator
    const response = await fetchUser(arg) // <-- supposed to be userID?
    return response.data
  }
)

I assume that the argument for fetchUser is supposed to be the same as the first argument in the payload creator.

Course URL: https://www.codecademy.com/paths/front-end-engineer-career-path/tracks/fecp-redux/modules/redux-middleware-and-thunks/lessons/managing-promise-lifecycle-actions/exercises/using-createslice-with-async-action-creators