Jonathan My guess is that a lot of things from MasterCard are optional and that these are mandatory for Maestro.
Like the adverts you see on the TV from the MasterCard company claiming that your purchase is insured. That's not true for the MasterCard that bunq provides either. At the end they show a little text: check your card supplier for conditions. Pure misleading advertising in my opinion, but allowed due to the little text at the end.