Me? Why? I'm not allowed to tear down my monument anyway...
I would interpret it this way: at least on the street side, the new house must adopt the shape of the still existing semi-detached house. So height, roof pitch, etc. Presumably also approximately the width towards the street. In the garden, I would try to have more freedom of interpretation. But the architect probably has better ideas.
Yes, it's not mine either Ok... yes, well, that's how I would have understood it (so to your first answer) and that's how the surroundings look to me too – like you have to look similar at most towards the front, but most people build quite large towards the back. Although especially the neighboring house implemented that for me in a questionable way

. See photo (the circled house is the one we want to purchase)