This is linked to a special vehicle tax, called BPM, which is related to the CO2 emissions of a vehicle, which is the case for the vast majority of Dutch vehicles.
One of the Dutch tax regulations stipulates that refund of the car tax paid (BPM) is only allowed for Dutch BPM cars that have been exported to and permanently/sustainably re-registered in a EU/EEA country*.
The Dutch Tax authorities conducted an investigation in 2019 and concluded that exporting BPM cars to non-EU/EEA countries is not allowed and may result in additional taxes.
* Austria, Belgium, Bulgaria, Cyprus, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovenia, Slovakia, Spain, Sweden and the United Kingdom.