I don't think it's the URL as much as it is the Default office render now rendering 270+ file types. Try slapping &download=1 to the end of the URL, this will cause it to work like a downloadable / linked file vs. a rendered file.
Yeah, seems they have a way to detect embed's now and restrict it with new formatting. You can turn off the "Short" Url to cause the old URL's to go back to how they were. But not sure how long that fix will stay viable.
Actually @Juan Carlos González Martín just tried in a inprivate session from another SharePoint site and no bueno, only works if you are logged into tenant not anon :P.
