Unless I am misunderstanding, that behavior is VERY different than what I've seen (I'm still on AutoActiveRE, unfortunately)
If you use a 25mil line width to draw your planes, the copper will not be able to fit through the spaces between through-hole vias
(unless you use an absurd via-to-via spacing rule) .
The planes on our designs would look more like swiss cheese than good copper fill.
There HAS to be a way to set a smaller aperture and still have a solid plane
sorry I could not help you,
Jack (aka "the new guy")