Example: I want to update 4 posts with 1 form. I cannot do it because I can only update post metadata of a single post using one form.
2nd Example: I want to create 4 posts of different post types with 1 form. I cannot do it because there is only one option for me.
I posted this already in a different thread: Adding Pro Forms Actions trough the Node Editor is in our roadmap 
This brings also the advantage to create multiple actions of the same type, which currently is a limitation due of the nature of the native Bricks Form, which has been extended by Pro Forms 