Because production orders are grouped to optimize the resources.
Also not all production order can be link to a sale order. Some are created because they are needed for another production for example.
They have this information because there are planned dates.
This production supply wizard manage that computation. And it takes care of the dates.
Your way of seeing the production workflow is without any automation nor computation. This is not the way Tryton is helping here. It computes and plan the production according to the dates of everything (customer shipment, supplier shipments, other productions etc.).
So if you want to see the plannification for a product, you have to look at the “product quantity by warehouse” view.
No they do not need to know that. Such computations are quiet complex to be seen as a simple one-to-one relation. But as I said, you can look at the evolution of the product quantity.
You are not going to manage that manually. Tryton does this for you.
No, you do not need to know that. This is wrong and counter productive to try to know that.
The customer will be delivered at the date the shipment is planned. You do not need to look at any production order.
But they are wrong. So Tryton is about good practice, not answer to all the wish.