UPDATE
In VS 2015 / Update 2, the behavior is that two scrollable sections appear when the expanded height exceeds a certain limit. In order for these sections to disappear / merge into one, it seems enough to just collapse some of the tree nodes, so that the height falls below this magic limit.
[Original post follows]
Was there the same problem (I am running VS 2013 Pro update 4)
No user interface parameters were found that would fix it. So I decided to just “learn how to live with him” and started making actual changes (ie include / exclude elements, “Undo, compare, etc.”), and suddenly noticed that he was back to this “high representation” by itself! And it is still in "Tree View" mode:

I assume that this was a transition of some elements to the Excluded Changes section (which for some reason became empty - it was not earlier). I didn’t understand that I actually did the trick, but this seems to be the most likely reason.
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