Single-family house 172 sqm with garage and sauna

the eaves point has been cited and defined like this in our development plan,

It is quite common for a development plan to define the lower reference point of the eaves height: in unfavorable cases, for example, as the penetration point of the (original!) terrain in the middle of the street-side eaves facade, and much more practical than the upper edge of the finished floor of the ground floor – though usually again within a tolerance range indexed to the average street height – or most unambiguously as a fixed reference height individually for each property. All of this falls within the competence of the development plan (local law), but the fundamental definition of the upper measurement point remains, from my perspective, a matter of higher building regulations and is established as a virtual intersection line between the outer side of the exterior wall and the roof covering. Therefore, I do not believe in a local special rule here.