Well, apart from whether it's legal or not, I'm just wondering why LH feels they need to do that.

I mean this seems completely arbitrary and it just leaves a bad impression if that's how they treat loyal customers. In the end their cost is going to be the same whether I book from DE or NL and whether I get an all-W fare or an E/T fare.

Edit:
And on a related note: Does anyone know why the flight search behaves completely differently on the German site vs the Dutch site? If I select "Search by price" on the Dutch site I get a nice grid overview on the following page showing the price for a couple of days prior or after the dates selected so I can see when it's the cheapest.

I don't get this option on the German site - whether I search by price or by date, I always only get a list of flights for the dates selected. Is there anything I'm missing?