There was once a not quite identical but similar case here.
A settlement of single-family houses was state-owned (50 years old) and was sold individually on divided plots to private persons a few years ago.
Due to a missing development plan, Par.34 applied, and since all houses were completely identical, there was hardly any discussion.
Then some owners wanted to build extensions, winter gardens, dormers, and double-wing windows and accordingly submitted building applications.
Apparently, the city suddenly realized that there was no development plan and subsequently postponed all building applications until the development plan was implemented. Duration was about 2 years and none of the owners could do anything during that time.
With the information you wrote, it also sounds to me that the development plan is to be pushed through first before any building permits are granted.
Whether that is legal, I unfortunately do not know.