The point is not promised date! Everyone knows that Apple Watch launch was a huge disappointment. If you cant fill the first hour of orders, then you are not ready to launch the product. I cant start a hot dog stand with pack of hot dogs and tell people that are waiting and paid for to come back in a month and I will have them. Another thing, they need to treat their customers better. Tim Cook should go out public (create a video), and post it on the website and explain why they are so behind so people would feel better. Give customers more information.
They could have changed the release date to say July when they would have more than enough of ALL the variations of watches. Would you rather chance ordering in April and maybe not get it until late May because of short supplies of that model, or would you like to wait until July?
There are plenty of other products be other companies that have not had supply to meet demand. Think of the hottest Christmas presents with people trampling and fighting each other to get the last one on the shelf. I'd much rather order online and wait then fight the crowd.
Also, before you purchase, the Apple did show the anticipated shipping window. If that was unacceptable, you could either no complete the purchase or wait until they are available online or in store to make your purchase. There are many other sites that will either tell you an item is back-ordered and either not let you buy it or not give an anticipated delivery date or worse yet, let you buy it then send you an email later saying it's unavailable and will be delivered as a later undetermined date.
You also have not paid for anything until your item ships.