I see your point. But if the shareholder declares the company to be at an end, the remaining provisions of this section could not possibly take effect, because there would be no company to implement them. Nor is there, anywhere in the Articles of Association, any provision for a shareholder to do such a thing. Look at what wienergriessler sent in #6:
nur, wenn der Gesellschaftsvertrag diese Kündigungsmöglichkeit ausdrücklich vorsieht. Schweigt der Gesellschaftsvertrag zur Frage der ordentlichen Kündigung,
The Gesellschaftsvertrag does indeed 'schweigen' on this point, so that only an 'Austreten' is relevant.
My impression is that whoever drew up the Articles simply included these words as a matter of form.