When he overlaid the gray boxes over the tracks I thought “that’s a VI!”.

I’d like to point that LabVIEW is not doing any of the fancy type stuff explained here (Either, Maybe, etc). It’s just that VIs (or functions in common parlance) can have multiple inputs and outputs, and LabVIEW’s graphical approach lends itself well to this use case. But LabVIEW’s type system is fairly primitive.