No, it's optional.
If there are only a few shipping/return locations you need to create, it should be more efficient registering through the seller portal (WING).
Please note that to do bundled shipping, the relevant products need to be from the 'same shipping location'. If you want to use the bundled shipping feature, you need to register the shipping location through the seller portal (WING) or API.
If you want to register products without registering return location, you can enter "NO_RETURN_CENTERCODE" as the return location in "Product Creation API". Please refer to the link below for more details.
Go to Product Creation API