Terrace roofing semi-detached house

Hello everyone.

My girlfriend and I wanted to have a terrace roof (3x5m) built on our semi-detached house with great joy. We asked the neighbors if they agreed and would sign that we would fall short of the minimum boundary distance of 3 m. They immediately agreed.

I then inquired at the building authority, and since the roof is exempt from approval due to its small size, we were supposed to have a so-called attachment construction burden registered.

We then submitted everything (company drawings (3d and 2d) as well as a cadastral excerpt with the drawing of the roof.

Then the call: We could not do it that way because (hold on tight) we are actually keeping a larger distance to the boundary / house edge than 50 cm.
Our option remains that we either attach it in such a way that the distance is not greater than 50 cm. This would mean that the roof, since it is not as wide as the house wall, would only be mounted on the left and the terrace would remain uncovered on the right.
The second option would be a wider roof, which, however, would exceed the costs.

I do not understand at all why it would be a disadvantage for anyone if we keep a greater distance than 50 cm to the house edge / boundary of the other semi-detached house.
Where is that stated? Wouldn’t the neighbor rather be glad if we are further away instead of closer?

I am at a loss and therefore open to advice.

Thanks and many greetings from the (still) sunny North

Where does it say that?

I am not very familiar with the details in NI, as the regulations (§5 Lower Saxony Building Code) differ significantly from those in NRW, but an attachment easement (or Anbaubaulast?) serves to allow the neighbor to build an extension (50cm distance is apparently still considered an extension with you). You can inquire with a local architect or contact a surveying office to see how they assess the situation; from here, I consider action against the authority to be hopeless.