Actually, you do (at least from an api pespective). If you have ever created a new listing and the "option" says "Default Title". Every product has a "primary variation", even if it isn't color or size. Although, the condition should be specified in the primary listing.
That being said, Shopify's Build in Google Shopping app is limited with being able to troubleshoot for such issues. It is reasons like this that we have many Shopify clients that use us, not just for google, but for other marketplaces.
