Update: I called again and pushed for an answer and I got it. Unfortunately, the answer confirmed what it's been said in various channels. Shopify does not support Amazon's GTIN exemption, therefore or you create the products on Amazon without a UPC and then link the products with shopify so you can synch the inventory and see the orders OR you add a UPC so you can publish from Shopify. Yeap! that's a shame, hopefully they will include the feature in upcoming releases.
I was going to start listing my products on Amazon this year. UPC exemption in place. Found out that there is no way to list without having to go through a third party app or paying for UPC. This is unacceptable!!! Shopify needs to fix this for its customers because it is too dang time consuming and expensive.