You could say Redux is a more constrained subtype of the 'single data flow MVC' you describe, which in turn is a subtype of 'all definitions of MVC which have existed'. In Redux actions are serializable, which opens up a bunch of other possibilities. Not to say Redux invented that idea by any means (it's the FP principle of separating data and behavior, also the OO command pattern), but it's useful to have a name specific name when talking about a more specific combination of ideas/constraints, especially if those constraints make different things possible (undo/redo, replay, logging/analytics for free).
You could say Redux is a more constrained subtype of the 'single data flow MVC' you describe, which in turn is a subtype of 'all definitions of MVC which have existed'. In Redux actions are serializable, which opens up a bunch of other possibilities. Not to say Redux invented that idea by any means (it's the FP principle of separating data and behavior, also the OO command pattern), but it's useful to have a name specific name when talking about a more specific combination of ideas/constraints, especially if those constraints make different things possible (undo/redo, replay, logging/analytics for free).