That is not what "end-to-end" means in this context. In fact, finding out yesterday that Outlook sync is not end-to-end encypted prompted me to look up OneDrive to see if it at least has that feature. It does not, and someone who doesn't know a thing or two about how cryptography works would have a hard time finding out that it does not, because the search results are polluted with people misunderstanding the concept exactly as you do.

Microsoft's own web site goes to great lengths to explain how all your data is encrypted in transit, and encrypted at rest. Their internal security and access control systems are elaborated on in impressive style. You'd think that if they're going to go to all that trouble, and want people to trust them, they would indeed provide end-to-end encryption where it's appropriate. But no, they carefully avoid mentioning the concept. They are unwilling to acknowledge that it might be a thing people expect these days, but they do not go out of their way to correct people who imagine that they already have it.