Microsoft seems to be toying with two different versions of the simplified ribbon. On the picture above, for example, Word Online has the more modern looking UI for the ribbon, while PowerPoint Online and Word Online below has a different, slightly modern ribbon UI. The former is the simplified ribbon Microsoft announced back in June, though the latter isn’t too different either:
It’s more than possible Microsoft is trying out these two different versions to see which one works better for users, so we can’t really tell what the final ribbon will end up looking like after the test is done. Adding to that, the new simplified ribbon isn’t available across all Office Online apps either — some people I have contacted have it on Word and PowerPoint, while others are only seeing it on OneNote or PowerPoint, etc.
After all, this is a slow rollout — so we really just have to wait and see how Microsoft proceeds with the testing here.
Story Source: Thurrott