I'm very disappointed that you have to be a single premium user to recieve this offer... I suppose the extra money for the family plan isn't enough? At least you offer it to some existing subscribers, and not just the new ones.
I looked at some posts from US costumers who had the same problem back in December/Jan. Looks like they got a link sent or the functionality was added by spotify to allow premium family plans to receive a google home.. hopefully we will too!