Yes, it is obviously a new development plan. There is also no development plan for the houses nearby. Apparently, construction was carried out there without a development plan. I suspect that this was easier historically. The municipality told us in any case that the district would not allow a development like the one we planned without a plan (which the district also confirmed upon inquiry).
Basically, the practice of building according to §34 could also be continued. Accordingly, these new building plots could also have been accepted in this unplanned inner area. Presumably, this did not happen because of the previous use as grassland / fallow land, and the scope of the new development plan only came into effect through incorporation into the new inner area. By analogy, my suggestion of comparing it with the neighborhood’s development plan then applies accordingly to what has factually arisen within the framework of the integration requirement there – practically as the question: "Which parts of the development plan would the neighboring houses not have fulfilled?" I suspect that essentially they oriented themselves to them and only additionally considered hedgehogs and insects. However, if there are significant "changes," the question of why arises and is worthwhile.
Unfortunately, I do not have a justification for the establishment...
How far it should already have been formally published in the establishment or public display procedure, I am not sure. But a justification regularly precedes a plan establishment – some development goal must make the plan appear necessary, and clearance under fences for hedgehogs alone would not be significant enough. The promotion of solar thermal energy and the exclusion of gravel gardens are certainly more important. Why offset shed roofs are banned here, however, is not clear to me.