bbPress uses its own internal actions to help aid in third-party plugin development, and to limit the amount of potential future code changes when updates to WordPress core occur. These internal actions can be thought of as “sub-actions” and allow you to add or re-order WordPress actions as necessary for plugins that depend on bbPress.
These actions exist to create the concept of ‘plugin dependencies’. They provide a safe way for plugins to execute code *only* when bbPress is installed and activated, without needing to do complicated guesswork.
bbPress is completely self-sufficient within WordPress. You can load it anywhere or in any order from any place.