Shipping rate options at checkout allow for perceived opt out
Customers can deselect, and therefore remove, their shipping cost from their visible calcuation on the checkout screen by selecting "-Choose a shipping method-" instead of the default rate or other rates that show in the drop down menu. This should not be an option. It implies to the customer that they can opt out of paying shipping - they can't - the cart does ultimately charge them. The selection of the prompt should not change the calculation, for any reason.
Aiming Higher Quantum Success Co. commented
This sounds more like a bug to me...