So this issue isn't explicitly new to VBox 6.1, nor Beta 2. But this is the first time that an Invalid Setting Detection warning appeared so I'm bringing it up again here specifically addressing this new requirement.
With Graphics Controller set to VBoxSVGA in a Windows 10 client with Office 365 installed locally as an application. The graphics controller is unable to render the Microsoft Office applications. I am attaching my logs and my configuration for review.
FYI, don't be worried about the name, it's just for labeling purposes with testing desktop configurations.