The default supply-demand dynamic doesn't generally apply to urban real estate. Supply is very slow to react to market changes, and is limited by all sorts of things that aren't price. In a lot of cities, prices (within reason) don't really affect supply at all.

First, building takes time and houses last a long time, so supply is unlikely to grow by more thana couple of % pa. Second, most of the space is taken and/or limited by planning, not price. Changing planning policies and improving transport is what actually gets a city with 250k houses to 300k.

Often, you'll find that people don't actually want the city to change/grow much and prevent it politically

The upshot is that is a supply-insensitive-to-demand market (the opposite of the cocaine market, economics teachers like for examples). If demand goes up, prices go up. Supply stays about the same. The inverse is that if price is held artificially low, this doesn't really dampen supply much.

Imagine manhatten house prices doubled tomorrow. How much extra housing do you think this would lead to?

All that said, this sounds like cheap politics. Developers complaining? That's probably a political point in amsterdam. It tick the do something box. Upper middle class people will get their new house a little cheaper (less competition). The new neighborhoods will be more middle class (and ethincally dutch), because owner occupiers tend to be these things. The rental market will be marginally tighter, as this grows the own/rent ratio a little.