Hmm, I'm not seeing that behavior when I choose 5 downloadable patterns on my needlework site. I've got min/max/units set to 1/0/1, respectively for the product. I also have "show the cart after add-to-cart" (or whatever that setting is), so when I add 5 to the cart I get the cart displayed with 1 item and a message " A downloadable product — <product name> — was not added to your cart. Your cart can hold at most one download of each product." displayed at the top of the shopping_cart page.

Let me see what's up ...