I think that was the core function of node red! But like everything, it's evolving! The evolution of the link node to jump between flows was the first steps! The main limitations on linking to subflows was the control of the messages, and selecting to what instance the message should go! This node helps with that!
I believe that this node, or other's similar with the same concept, have the place and use cases! To use it or not, it's up to the end user!