In the namespaced schema, all types are automatically prepended using the PHP package's owner and name (in this case it is PoP_ComponentModel_, where PoP is the package owner, and ComponentModel is the package name).
Namespaces help manage the complexity of the schema. This is particularly useful when embedding components from a 3rd party, where we can't control how the types have been named. For instance, different plugins in WordPress may implement a Product custom post type (such as WooCommerce or Easy Digital Downloads); if they wish to create a GraphQL type for it, they can't just name it Product or it may clash with another plugin. Hence, they would have to manually prepend their type names with the company name (such as doing WooCommerce_Product), which is not the most beautiful solution.
Now, GraphQL by PoP enables to define an environment variable, and it will automatically prepend all types from a package with the PHP namespace used for that package (following the PSR-4 convention, PHP namespaces have the form of ownerName\projectName, such as "PoP\ComponentModel").
There are many more use cases where namespaces can be pretty useful, listed down in this GitHub issue.