"They" meaning "FBP-like" or "FBP-inspired systems", to use Joe Witt's terminology... They are usually control-flow oriented, and to my mind do not yield the productivity and maintainability advantages of the "classical" FBP paradigm shift. I recently asked Node-RED's Nick O'Leary why Node-RED only allows one input port, and the answer was something like "because we have never run into the requirement"... a) this is not something that can easily be added after the fact, without totally rethinking the product architecture, and b) trying to build complex systems without that feature would be, to me, like trying to hang wallpaper with only one hand! One litmus test I use is that of concatenating data streams using the two different paradigms - I tried to describe this in an article a year or so ago, recently updated: https://jpaulm.github.io/fbp/concat.html Cheers!