Restocking Existing Product At An Exact Time without Product Ever Not Being Live

We work with a fulfilment centre who are integrated with our Shopify. Once they book the stock in to their warehouse, the stock holding is populated against each of our SKU’s. However, we want to schedule re-stocks to occur at a certain date and time so therefore want the inventory in Shopify to remain at 0, with the items only becoming available to purchase at the time of the scheduled ‘product drop launch’. We do not want the product to not be live at any time because this enables customers to sign up to be notified when stock then is available. There is a way of creating a draft order, where you can ask Shopify to reserve the stock until a certain date and time, but this is not working how we need it to. Shopify is instead reserving draft order quantities as additional units and not deducting these quantities from the populated stock holding. Is there a way to achieve an automated solution to this? Why is Shopify not reserving the available/on hand stock instead?