First draft from the draftsman for our single-family house

Oh dear, you are now making me quite confused or uncertain about the slope. The draftsman simply mentioned 3m.. I assumed that referred to the entire property..

Next to our 2 plots, there is also a house with a (pushed-out) basement.

I’m happy to repeat myself for the 3rd time, as soon as we own the property, the first thing to be commissioned will be a soil investigation with leveling.

I’m attaching 2 pictures of the property. One from the street (looks rather flat there) and then from the adjacent property below looking up (you can already see the slope).

Maybe use this view for a better understanding?

Regarding the split-level: the mentioned house is less than 5 years old. Apart from that, I don't find the many (albeit smaller) stairs very appealing. It's certainly a matter of taste.

Maybe use this view for better understanding?

Certainly. That looks like only about a third of a story slope within the house depth. I don’t see a basement living area voluntarily there. But still, gladly a living room at the level of the garden side. Perhaps by means of a house entrance adjacent to an intermediate landing of the stairs, that is: with the front door at the height of what from the garden side looks like a "raised ground floor."

On the topic of split-level: the mentioned house is not even 5 years old

That can be exactly the problem if the architect is still young: then they are not familiar with such things and build the interpretation valid forty years ago: a somewhat harshly speaking all-room fragmented into half levels.

My parents-in-law built their house 40 years ago. The architect maybe considered the noise development with 3 children.

I think it depends on how the levels are designed.

Kitchen, dining, living with WC is, for example, one level at my parents-in-law's.

I think in the end you don't necessarily walk more stairs.

Don’t let yourself be confused by any speculations. What you don’t like, doesn’t have to be. But you guys have a tendency that can also be used. If you don’t build upwards, then just downwards. In the end, it amounts to the same thing, just a bit more thoughtful. If you stay modest, even a private room can have 30 sqm for family members in need of care.

All in all, you don't necessarily end up walking more stairs.

That largely depends on the distribution of the rooms and their functions.

But I don't think we have a classic case of an obvious split level here. This "problem" reminds me – although with the slope direction reversed – of this case from the summer: