Cocoa: Maximizing a size-constrained window makes it smaller that the minimum size

Clicking on the zoom button on the window that has size-constraints on one axis maximizes the window, however it becomes smaller than the allowed minimum size.

For example on the standarddialogs example if you open any of the QInputDialogs and click on the zoom button - the window zooms horizontally, but vertically of becomes a little bit too small to fit the content.