ᐅ Knee wall height generally 1 meter, door threshold, construction plan / building permit

If the building plan includes the requirements you mentioned, then it makes little sense to question the logic of the plan. No one is forcing you to build there. Sometimes municipalities just have unusual ideas about urban development.

... with zoning plans, it is also important to know the exact wording in order to interpret it correctly

3.1.7
Knee wall (Exterior wall height of an attic space between the top edge of the upper full-story floor slab and the lowered bottom point of the roof structure raised to enlarge the attic space)

The allowable knee wall height for gable roofs and staggered single-sloped roofs (note: other roof types are not permitted) is uniformly 1.0m (3.3 feet).

Yes, it does read that way. Strange! There will be significant height differences. Two full floors plus an attic with knee walls will also look strange proportionally...