Hey Steven!
This is technically a gameplay issue, but I check it on several parts - how many do they literally sign? It is possible there's a foreign bias look at this season:
Ajax buying 3 Dutch players and 8 Foreigners
Feyenoord 6 Dutch, 10 Foreigners
PSV have bought 6 Dutch, 3 foreigners - but I remember a German (speaking) invasion under Schmidt