Looks like the legal team reached out and said that making monochrome icons isn't allowed [0]

0: https://github.com/simple-icons/simple-icons/issues/11236

That's really a shitty move from MS. But, technically, since they're still in the commit history, you can retrieve them for personnal/private use.

very interesting

Adobe seems to have no problem selling monochrome logos of Microsoft products

https://stock.adobe.com/search?k=ms+word&asset_id=595866420