But that's hardly unique to Adobe. Any document format that allows (arbitrary) other things to be embedded is subject to that. A Word document with other things embedded in it is no different. (Just like correctly rendering or editing an OpenDocument file would require you to implement half of SVG and MathML – while they're open specifications it doesn't necessarily mean you have an implementation at hand you can use.)
But that's hardly unique to Adobe. Any document format that allows (arbitrary) other things to be embedded is subject to that. A Word document with other things embedded in it is no different. (Just like correctly rendering or editing an OpenDocument file would require you to implement half of SVG and MathML – while they're open specifications it doesn't necessarily mean you have an implementation at hand you can use.)