When I submit a product feed to Google and a SKU is marked in stock, how does Google verify that? Is it a human looking over a given PDP and checks if that SKU is in fact in stock or is it an automated process?
Product feeds are verified through matching against structured data on URLs, listed in product feed as product URL. If you activated automatic updates, so Google will prefer current structured data from the product URL. More here: https://support.google.com/merchants/answer/6069143?hl=en