Sure it does. I'll give you it does not say why they chose it over other alternatives which I'm thinking is what you are looking for. Are there really any alternatives? The only real alternative I can think of is OpenDocument Format and I don't consider it alternative. As they say on that page, 80% of their users already deal with DOCX so 80+% of them will have to convert to ODF. I can't imagine ODF having any sort of benefit worth requiring most people to convert their documents before sending.