“Flat is better than nested” - for data as well as code?

This question got me thinking: should we apply the principle that "flat is better than nested" to data as well as to code? Even when there is a "logical tree structure" to the data?

In this case, I suppose it would mean representing children as a list of IDs, rather than an actual list of children, with all the nodes in a single list:

[ {'id': 4, 'children': ()},
  {'id': 2, 'children': (1, 7)},
  {'id': 1, 'children': (6, 5)},
  {'id': 6, 'children': ()},
  {'id': 5, 'children': ()},
  {'id': 7, 'children': (3,)},
  {'id': 3, 'children': ()} ]

(I used tuples because I prefer not to give myself the flexibility to mutate an object until that flexibility proves itself to be useful and usable in a clear manner. In any case I would never use None here instead of an empty sequence, because it complicates the logic, and "special cases aren't special enough" - here, it isn't special at all.)

Certainly this is shorter, but the tree structure is obscured. Does that contradict "explicit is better than implicit"?

Personally I find that "flat is better than nested" is of limited applicability, and nowhere near the most important aspect of the Zen. (Certainly I could not do a lot of the nice functional-programming things that I do if I didn't allow myself significant nesting.) I suspect that the problem with "nested" is that it requires context switching when you comprehend the information. I really think this is more of a problem when following imperative logic than for parsing data or functional-style code - where it's easier to just mentally name the nested block, and consider its workings separately from the outer context.

What say you?