Turns out you're right, I was working from app notes which were trying to sell sync bucks. (Not that that's hard to do, sync bucks are awesome.) I do think there are a few pathological startup cases that get easier when the output can sink current, but while those cases are easier to get into with bipolar rails, they still ought to be quite rare.

Just want to say both of these responses are awesome. Sent off a kicad file to OSHPark for a dual +/- 15V supply using the same circuit twice. Will see how it works out :-)