Is this an expansion joint?

Hello everyone!

We intend to buy a house. Next to it is a garage which was solidly attached. Now you can clearly see a crack between the house and the garage. The owner explained to me that this is an expansion joint. When building stone by stone, you have to do that, according to him. The surface on the garage itself is used as a terrace. On top around the entire outside area lies a thin layer of stones, I guess so that the water can drain?

Expansion joint or not?

Attention layman's opinion:

I believe this is an expansion joint. Fortunately, the garage is not connected to the house. But what is much more important: look at the terrace, where does the standing water flow? Hopefully away from the house. Definitely bring in an expert. That would be my approach anyway. Nothing is more susceptible than roof terraces.

I would first ask myself what is sagging / has sagged there. And whether it will continue. The house or the garage.

I would also no longer call it a joint. From the way it looks and how the seller talks, it is almost a predetermined breaking point.

I know expansion joints as something that expands depending on the weather, but correspondingly also contracts again.

The garage was not built so crookedly attached.

And the question about water during rain is justified. Is there anything sealed on top of the "joint"? What do the interior walls of the garage and the house say at these spots? Are they coincidentally freshly painted?