Why is MediaMarkt so flexible with ecocheques but Coolblue and Vanden Borre aren't?

Sorry for the incoming rant but I'm done with ecocheques.

I went to MediaMarkt to ask if I could buy a certain product with ecocheques. The guy replied "you can buy anything with ecocheques as long as you add one ecocheque product (e.g. a lamp). If you want to return the ecocheque product, you will received a Mediamarkt gift card".

I went to Vanden Borre and there you can only buy ecocheque products and if you want to return it, you get a giftcard specifically for ecocheque product. Same with Coolblue. How come Mediamarkt is so flexible?

In case anyone knows a shop close to Antwerp where I can exchange an ecocheque product for cash, let me know. I want to be rid of my ecocheques and since I have a gift card for VandenBorre I have to go to that shop to buy the product I want.