--> [A] --> [B] --> ------>
Either of these is a consistent choice in itself, but they don't play well together as part of the same diagram unless rigorously separated.
A different point is that some high-level abstractions do have a fairly natural visual representation. This even includes the "functors" and "monads" that are well-known in FP. In general, one should not be surprised if category-theoretical abstractions turn out to be representable in this way. (Many visual languages actually turn this into a source of confusion, by conflating operations on an atomic piece of data with operations on a stream or sequence of singular data points. A stream is a kind of functor, which is why it (with its peculiar operations) is endowed with a simple representation in dataflow. But there are other functors of interest.)