I can also confirm it doesn't, I found the exact same issue while trying to generate a 25kx25k world with symmetrical poles and equator exactly in the middle. After 5-7 tried I gave up. I would also much appreciate something like "real earth" option that would always generate poles only on the north and south end of the world and the equator always, and only in the exact middle of the map - no matter the selected map size of starting biome.
The world creator is amazingly configurable but somehow it completely omitts this specific setting.