Microsoft Office Online switches to OpenDocument as default format

So earlier today I was trying out Microsoft’s online office suite and noticed something interesting. Whenever you create a new Word, Excel, or PowerPoint file from the OneDrive interface, it automatically creates it using the OpenDocument file format (odt, ods, odp) as opposed to the Microsoft Office format (docx, xlsx, ppt). Interestingly if you create it from it uses the Microsoft format instead.