Thank so much @Alan_G . In our case, per this thread: Urgent: Product GraphQL API bug? Suddenly getting "Variable $input of type ProductVariantInput! was provided invalid value for inventoryItem.sku (Field is not defined on InventoryItemInput)"
One of the endpoints in 2024-07 that we rely on broke in the last 48 hours and apparently won’t be fixed, so it’s time sensitive for us to find a resolution for this specific default variant behavior in 2024-10 that doesn’t involve an unreliable workaround.