It is a change of behaviour, I believe related to the fact that Word 365 is aimed at working on a variety of platforms. If you want the documents to always open in a particular view, you could add an autoopen macro
to the document to switch the view and save the document as macro enabled e.g..
Code:
Sub AutoOpen()
ActiveWindow.View.Type = wdWebView
End Sub
http://www.gmayor.com/installing_macro.htm