If they're exporting crops that's about feeding somebody. People who would have to try to get their food elsewhere and have to worry about the standards/quality of those new sources. It's even perfectly fine for people to grow and sell flowers. There may be ways to make it more efficient, and maybe the government should be encouraging that so they can buy up some of the saved land, but I'd bet there are ecological consequences to paving over flower farms too.
Economically it would make more sense to import food from France, Spain etc. it would reduce the cost of living for the overwhelming majority of people with limited negative economic impact.
The Netherlands is completely tiny compared to many of the countries people are coming from, and the land is allocated. You can't replace the farms with suburbs throughout the country, and even if you did, then what? Is it allowed to be full then? Or should people still leave their much more land-rich origins to come anyway?
Does EU have the USA problem where most farmers are basically sharecroppers where they are mandated where they can buy their seed, buy their fertilizers, where they buy their chicks/sows/calfs, what equipment they can buy, how they can repair their equipment, where they can sell their crops, and at what specific prices all from a single undemocratic corporation?
In the USA it's basically corporations that run everything and drive the farmers into poverty where said corporations can then buy their land and rely on undocumented workers to keep the abuse going.
From the outside EU farmers seem to have better labor relations, but don't know.
Swiss here, living in a small town quite close to farmers. I would expect if it was the case here, I would have heard about it, given my proximity. I'm aware of this "arrangement" in the US, never heard of it happening anywhere in the EU - I haven't done a comprehensive study though, maybe someone with more knowledge can say more.
Considering EU farmers tend to riot with their tractors in the capitals of countries which try to control them I doubt it.
AFAIK Norwegian farmers fear of things like this was what kept Norway out of EU even with two referendums (or at least one of the distinguishing factors).
If anything agriculture is going to require more land in order to be sustainable.