A number of Titanium APIs show a wrong 'Defined By' information. This is mainly happening for those APIs that are inheriting properties or methods.
In the sample above, 'backgroundColor', for example, is not specifically defined by Titanium.UI.Button, but inherited from Titanium.UI.View (as correctly displayed in the Docs: http://docs.appcelerator.com/titanium/latest/#!/api/Titanium.UI.Button-property-backgroundColor).
This information should be taken from the docs - in this case I would expect to see 'Titanium.UI.View' instead.
See also attached screenshot.