You can create GH definitions without using any graphics, writing code with text, and any FBP language can be represented with graphics, you only need an entity that draws the component. This is because language is more than you think, it is not only a representation of the content of a system (syntax), it is also the communication rules of a system (grammar). The same language can have several ways to be represented. Besides, you cannot adequately understand a programming paradigm, which is what he asked, without the concept of language, as a concept, not as an implementation. Programming is communicating with computers.
In this case, you can use the input-process-output form as if it were your word in your language, and even if you do not include an image, it is still a graphic paradigm because it is 100% compatible with visual representation, due to how simple it is. Y that’s why is so limited.
You make it more complicated than it is. So many nuances are not necessary. This is something very explicit and easy to understand. Flow diagrams, connect nodes from outputs to inputs. What you say about thinking is algorithmic thinking, it is a paradigm of thinking, not programming. But confusion is normal if you ignore the context of what you define. And by the way, you as a human have a much more complex way of thinking than a flow diagram. Humans are not so basic, perhaps our way of representing yes, but our brain is not. Our human way of thinking is more similar to liquid state machines or eco state machines, which is the paradigm that graph-based database softwares use to represent and run knowledge graphs. Where instead of having a simple schema like input-process-ouput, we have entity-relation or other that include actions. It is another form of symbolic language, regardless of its implementation, because it allows you to communicate and represent everything using other principles more sophisticated. Being a symbolic language, like FBP, it can also be represented visually, with graphics, always.
EDIT: To clarify, all flow diagrams (understood as process connection, not as drawings) are networks but not all networks are flow diagrams, because there are networks whose circuit is not defined until you read or write, or networks that do not follow a directional flow, bc they behave like waves.
But that’s fine, you don’t have to see it like I do, it’s just an opinion that encompasses yours I think, because I’m not opposing you, just opening the field of vision.