All Europeans need to buy an Interrail pass so you are correct.

Hi @Jonas Lenz 

Interrail Passes are available to all persons in possession of a valid passport/identity card or a residence permit of one of the countries of the European Union and the countries listed hereafter, or persons officially residing in one of the countries of the European Union and the countries listed hereafter: Albania, Andorra, Belarus, Bosnia and Herzegovina, Faroe Islands, Gibraltar, Iceland, Kosovo, Liechtenstein, Moldova, Monaco, Montenegro, North Macedonia, Norway, Russian Federation, San Marino, Serbia, Switzerland, Turkey, Ukraine, United Kingdom and Vatican City.

Have a lovely day!