Products cannot be reserved in any way.
This applies both to products with and without a release date.
Adding a product to cart is not the same as purchasing or reserving it. The only way to make sure you get what you want is to complete the purchase.
Did you know?
If you choose to pay by credit card or PayPal, then you products remain "reserved" for 4 hours, just to make sure you complete the purchase without any hurry.