Does Amazon do Calculated Shipping Rates?

I just made my first FBA items about a week ago and decided to add FBM variants now too. I already sell a fair amount on eBay and Etsy and I’m familiar with how they handle shipping rates and orders.

One thing I’m confused about with Amazon – is there no way to have Amazon calculate and charge the actual shipping rate? I see in the migrated template I can set a base fee plus a cost per pound. But why can’t I just have it calculate based on the package size and weight of my item (like how eBay and Etsy work)?

Furthermore, the cost per pound to ship seems to be based on the item weight and not on the weight of the package I entered. For example, my item is only 2 ounces but when packaged for shipment it is 7 ounces. Amazon seems to charge the weight rate on the 2 ounces instead of the 7.