Hello,
In my opinion, there is not even a devaluation happening there. The defect is clearly outside the field of view and vs. with the usual viewing distance and angle hardly noticeable. However, there is a kind of film paint pen with which you can try to repair small scratches. Your window maker will, in my opinion, not do this.
I can understand your problems, though. When buying an apartment, the opinions of construction companies or developers and buyers often differ (speaking from experience on the part of the construction company). Fortunately, there are standards for this and ideally an expert at the acceptance who can clarify these discussions directly.
Best regards, Jann