[1] http://research.microsoft.com/pubs/179364/p61-mcdirmid.pdf
I certainly wouldn't call Excel or Access 'inherently hierarchical'. Neither do I see the connection between 'visual languages' and 'inherently hierarchical' languages. If anything, the majority of visual languages I can think allow placing arbitrary computation at any point between arbitrary data sources/sinks. Where hierarchy exists it is usually fairly flat and used for organisation or code reuse. Arbitrary data-flow between any level or branch of the hierarchy is also a common feature.
Excel has one level of nesting within a file, but Excel "programs" are not limited to a single file; and, in fact, Excel has features designed specifically for programs that require multiple files to be open at once to interact.
Its true that each level of nesting in Excel is different in kind so that Excel doesn't support arbitrary nesting of namespaces, and that different bits of Excel functionality support different degrees of nesting.
I would argue that relational is also effectively hierarchical if not intrinsically: even without nested tables you always have IDs tacked on in a column that refers to rows in other tables. And once you start doing that, well...object graph.
That's an interesting point. We explicitly avoid encapsulating state in that way, preferring views to interfaces.
> I would argue that relational is also effectively hierarchical ... object graph.
A graph is fine. The difference from a typical OO hierarchy is we get to start wherever we want in the graph and we can easily insert new edges anywhere in the graph, or hyperedges that relate multiple entities. It's not like a filesystem where you have to decide which property of the file is most important and gets to be at the top of the hierarchy.
Objects support references that give you pretty much the same thing. The ability to add new kinds of edges is more of a function of your object system. In a dynamic language where members are basically defined as a dictionary, you just add a new key-value pair to the dictionary.
It has sheets, but not subsheets (which are a feature of some other spreadsheet programs that you can find lots of questions online about how to do or fake in Excel; that being said, its still heirarchical, both in its structure and the visual metaphor for interacting with it.)
Even Kodu is hierarchical to a limited degree since each bot is programmed separately, but its not unlimited as in the other examples listed (which I would argue, is necessary to be considered hierarchical).