ZDEMO_EXCEL18 doesn't protect the workbook, what does it demonstrate?

[sandraros]

I don't understand what this program should demonstrate. Can anyone explain?
What means this cell with the text "This cell is unlocked"? In fact it's not unlocked at all. Unlocked cells are part of worksheet protection, not workbook protection (worksheet protection is demonstrated in programs ZDEMO_EXCEL17, ZDEMO_EXCEL22).

abap2xlsx/abap2xlsx#444 was closed a long time ago, but no explanation. I could verify that workbook protection works if a password is setup, but ZDEMO_EXCEL18 doesn't define one.