Most of the included fonts belong to other vendors, with the majority being Monotype. Many are also duplicates of what's already included with the OS, such as Wingdings, Times, Verdana and Arial.
That said, I have never checked to see if Microsoft specifically prohibits the use of their included fonts outside of Office 365. I suppose mostly because I have so dang many fonts of my own to use from my previous business doing prepress work, the only thing I ever did with those embedded fonts was to remove as many as possible without breaking the Office apps.
Now I feel compelled to look. 🙂
Edit: Hmm, still couldn't find a real answer. I could only locate a section on Microsoft's licensing here:
https://www.microsoft.com/licensing/docs/view/Licensing-Guides
The only close match is the PDF for Microsoft 365 for enterprise | Licensing Guide. Doing a search through that document, the word "font" doesn't appear even once. But then, the doc concerns licensing use of the suite, not the included components.