All of the payment side is handled by Plimus, so these are their requirements, not New Star Games'. I can only say this is common practice for this payment method for anything, and nothing specific to the purchase of this game.
Ultimately you need to trust Plimus to use this method. Having done a quick search I get the feeling that they can be trusted. I know NSG has used them for many years now.
#You can play your card, I'll hold onto mine, Tied up in the reasons, Ace take your time#
#Looks turn to lovers, flames into fires, Jack loves his tragedy, Queen her desires#