Currently the logic is hard coded to require authentication for download products so it will prompt the user to login automatically to complete the purchase. Other fulfillment types are currently hard coded to not require it but suggest it.
The plan is to add settings for other fulfillment types so you could require it or not according to your preference but it is not complete yet.
WebStore is in early stages of development, it is not yet a general purpose ecommerce solution.
The workaround to hide from anonymous is not really a security feature, it is just cosmetic, but it might work for you. You could add an instance of Html to the same page with instructions/links to login and set it to "hide from authenticated".