I just discovered something I hadn't run into before and hadn't seen posted here.

If you have the stock by attributes mod installed, it will export your variants to the feed.

However, since it was set up for Numinix's upcoming new stock by attributes, it does not work as it needs to and can/will get your products invalidated.

So if you have it installed, you are going to have to edit the googlefroogle.php file in the root.

Comment out this line by adding the // in front of it.

Code:
if (defined('TABLE_PRODUCTS_WITH_ATTRIBUTES_STOCK')) $stock_attributes = true;