It would be nice if Post/ProfilePostComment/Warning/ThreadReplyBan/etc would implement the ContainableInterface, as these do have container. Most of these could also implement DatableInterface.
Thank you for reporting this issue, it has now been resolved. We are aiming to include any changes that have been made in a future XF release (2.3.10).
Change log:
Implement ContainableInterface and DatableInterface on various child content entities