This applies primarily when beginUpdates / endUpdates is not used.
Due to user interaction-driven edits, like reloads or adding content
at the bottom, sometimes this is unavoidable in app design and thus
critical.
I have a diff in flight to make ASDataController / ASRangeController
robust against very aggressive thrash testing, which will be added
both to the unit test suite and this new example project.
c700618862