I think that might be a poor labelling issue
If I had to guess, I would say that iPhoto 5 does not use Dashboard, but instead features a dashboard. That is, what you would call the implementation is a dashboard (small "d") in that it's a collection of similarly-themed tools in a confined area, but that it does not use Dashboard (capital "D") which is the name of a technology to be included in Tiger.
Besides, the individual items in the Tiger Dashboard demo are called "Widgets", not "dashboards."
Perhaps he used the potentially confusing term to note that the iPhoto editing dashboard does have the "look and feel" of the widgets that he's demonstrated in Dashboard. Or perhaps everyone is right, that that particular feature requires Tiger. But I think it's the former. There would be disclaimers on the Apple site that say that the feature requires Dashboard.
I expect we'll get this widget without Dashboard. And when we do get Dashboard that it won't power this widget because this dashboard is not a Dashboard Widget or a but rather a regular widget that happens to be a dashboard.