According to this website it is strongly forbidden to fly over Oslo without permission. But my Mavic 2 Zoom with all latest updates reports only a restricted area which I can unlock without any confirmation from the authorities. Why is this not a "no flight" zone?

Hello there Paul Lenz. Thank you for reaching out and for giving out these information. For us to be able to assist you with regards to this matter. Kindly please send an email to our DJI FlySafe Department at flysafe@dji.com for us to be able to help you further. Thank you.

DJI is not responsible for air zones restructions, but support them only with FlySafe. Some of air zones are temporary you can NOT rely on the FlySafe only

Never rely on DJI's zoning system.
Trust the local (official) maps that the country itself supplies only!