My developer is telling me that all changes to items must be communicated using the (user created!) SKU rather than the (eBay created) Item ID. This seems crazy to me. Is it true?
I see the old API "Version 1157" suggests using the item ID but the new one "Inventory API 1.12.0" seems to require the SKU is used.
What are we missing? Why would eBay not allow identifying listings using their own Item ID?