The product types that are included in the Merchant Center feed (and if selected, in the optimized title) are derived from the categories on the connected website. In most cases, these category names are in context on the website and make sense to the user when viewing. In Google, the context is no longer there.
FeedOps gives you the ability to override these product types in order to match the way that people search. For example, if the category is "Kitchen", but the only products in that category are in the "Kitchenware" category, that is how people will seach for those products. It is then strongly recommended to override that product type in FeedOps.
This is one of the most important steps to ensure relevant traffic to the product landing pages, and all product types should be considered to be overridden.