This may not be a bug if the intent is for SceneBuilder 2.0 to be backwards compatible and completely replace SceneBuilder 1.1.

SceneBuilder 1.1 and 2.0 are installed as two separate applications. They get separate entries in add / remove programs and are installed to separate folders in "Program Files (x86)\Oracle". However, the SceneBuilder 1.1 installer refuses to install if SceneBuilder 2.0 is already installed. The installer complains that a newer version of the application is already installed.

In my opinion, it's better for 1.1 and 2.0 to be treated as distinct applications so the preview versions of 2.0 can co-exist, and be used selectively, alongside the stable 1.1 version. This works fine and both versions seem to co-exist without issue if 1.1 is installed first and the 2.0 preview is installed second.