Development plan with a statement regarding the height reference point on a slope!

After we were assigned a plot of land (new development area is being developed), we began planning. The development plan stipulates, among other things, the following: eaves height 4.5 meters, 2 full floors are possible, roof pitch 0 – 45 degrees. We are stuck on one wording: "Due to the hillside location, the height reference is set at the upper intersection of the building with the natural ground to avoid disadvantages due to the hillside location." The height difference of the plot is about 35 cm sloping downwards from north to south; the street side is on the west. And now to my question: What kind of planning flexibility results from this if we want to achieve the highest possible knee wall? I am grateful for any suggestions.

In practice, probably none. 35cm across the entire property is almost flat. And under the house, you then have a few centimeters less slope.

The wording simply means that you measure on the uphill side of the building.

"Due to the hillside location, the elevation reference is set at the upper intersection of the building with the natural ground in order to avoid difficulties caused by hillside conditions."

Finally something citizen-friendly.

What kind of planning flexibility results from this if we want to achieve the highest possible knee wall? I am grateful for any suggestions.

Gladly: then I’ll give you the suggestion right away not to want to make the knee wall as high as possible.
The wording of the specification is not meant, made, or suitable for flexibility. It is intended to and does avoid difficulties.
A eaves height of 4.5 meters will probably even allow a knee wall of 160 here; something around 120 to 140 is reasonable.