All of the lists in a Maniphest workboard need to be reorderable by dragging or some other mechanism. In the current scheme the only way to do this is by creating new lists, renaming existing lists, and dragging things all over the place.
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Are you at HEAD? This should be supported now: Manage Board > Reorder Columns. Here are some screenshots from this install:
I'm guessing this list just got written before column reordering, but let me know if I misunderstand.
(The UI is a bit rough still, but should work OK.)