Impacted versions: 9.0

Steps to reproduce:

* Create an MTO product with 
  * Product Type: Stockable Product
  * Routes: "Buy" and "Make to Order"
* Update Qty on Hand to any quantity (i.e, 2).
* Create a sales order with this product and a number <= to the one in the step before.
* Confirm the sales order.

Current behavior:

The created delivery picking appears in state "Reserved" and the current quantity on stock has been reserved, allowing you to transfer that stock.

Expected behavior:

The created delivery picking should be in "Waiting another operation", or at least in "Waiting availability" until the purchase order is confirmed (if you have defined a supplier for the product and the procurement creates the purchase order), which seems to be the current behavior when there's no stock available (is this also correct, as it allows to manually reserve?).
while loop:
                pack_quants = pack_obj.get_content(cr, uid, [test_pack.id], context=context)
                all_in = True
                for quant in quant_obj.browse(cr, uid, pack_quants, context=context):
                    
                    if not quant in quants_to_compare:
                        all_in = False
                        break
                    else:
                        
                        if not pack_destination:
                            pack_destination = quants_suggested_locations[quant]
                        elif pack_destination != quants_suggested_locations[quant]:
                            all_in = False
                            break
                if all_in:
                    good_pack = test_pack
                    if test_pack.parent_id:
                        test_pack = test_pack.parent_id
                    else:
                        
                        loop = False
                else:
                    
                    
                    loop = False
            if good_pack:
                top_lvl_packages.add(good_pack)
        return list(top_lvl_packages)
    def _prepare_pack_ops(self, cr, uid, picking, quants, forced_qties, context=None):