Importing and Returning Value Parameter in Exercise ITAB BASICS

In the part, when we sort the updated table, why does the Importing parameter inside the method sort_itab got changed and received the value of the updated table?

Should updated_data not be overwritten by the initial_data (6 entries from method fill_itab)?

I don’t see in method add_to_itab something like initial_data = updated_data.

METHOD sort_itab.
updated_data = initial_data.
Sort updated_data by group ascending number descending.

Many Thanks