Amazon free upgrades to priority and courier deliveries to Australia

This is the 2nd time it happened to me and I think they may have an unadvertised policy to offer shipping upgrades on orders which somehow don't get shipped right away or within 2-3 days after an order is placed.

Order #1 (a few sheet sets)

• Day 1 - placed order and chose the cheapest shipping option
• Day 4 - items shown not shipped on order status page
• Day 4 - emailed Amazon and they upgraded the order to priority shipping for free. Essentially, I paid zero shipping on this order and got it at the same time they were supposed to arrive if items were shipped as soon as they were ordered.

Now it gets even better in the second instance.

Order #2 (iRobot Braava)

• Day 1 - placed order and chose the cheapest shipping option
• Day 4 - item shown not shipped on order status page
• Day 4 - emailed Amazon and they upgraded the order to priority shipping for free (same as last order)
• Day 5 - order still not marked as shipped but 'change delivery speed' will still let me change the delivery service and now the courier option (fastest and most expensive option) is available for $0 as well (which was $70 odd at the time order was first placed)

2nd order was received today via DHL within 4 days of changing the option to free courier upgrade.

I am thinking Amazon makes these options available for all orders that get delayed at the shipping stage but instead of automatically making them available to customers, they leave it for customers to find the option and take it.

Anyone else had a similar experience?