I think it caused more problems than it was worth. It generated a lot of "why doesn't my program work?" questions.
It's one of those things not all systems support.
public static final StageStyle UNIFIED
Defines a Stage style with platform decorations and eliminates the border between client area and decorations. The client area background is unified with the decorations. This is a conditional feature. If the feature is not supported by the platform, this style downgrades to StageStyle.DECORATED
` NOTE: To see the effect the Scene covering the Stage should have Color.TRANSPARENT