Detached semi-detached house

That is not the color, in my opinion, that is the plaster. And the plasterer messed it up. The roof moves and was firmly connected to the plaster. And somewhere it has to crack. This is damage, but nothing that couldn't be fixed and certainly not something that would cost thousands.

On the other hand, what advantages does it have?

It's not about advantages. It's being treated as if it were something special or technically more complicated.

If you cannot attach a semi-detached house to an existing one, you are technically incompetent. Constantly claiming otherwise doesn't help.

Non-twin semi-detached houses and also uneven row houses are quite common. Take a walk through an old, developed village and not always just new housing developments.

Nothing is more boring than a housing estate where entire streets of houses look the same.

And I know many development plans where no specifications for row houses and semi-detached houses are made specifically because they explicitly don't want this uniformity.

If you cannot attach a semi-detached house to an existing one, you are technically incompetent.

But you can be so technically competent that you understand the practical consequences of the dizygosity of twins.

I noticed that there is a gap at the corner on the inside of this wall... As you can see in the photos, I can fully insert a 0.5 mm thick measuring tape... Is that normal? Shouldn't the corner be sealed?

Here is a better photo where you can clearly see that the gap is open to the outside... You can also see on the outer wall where the gap is... Disaster?