This is nonsense. The uploader is not necessarily the copyright holder of the code. The uploader is not necessarily in a position to grant extra rights above the actual license.
What happens if someone else uploads my code to github?
What happens if proprietary code is uploaded to github?
What happens if national secrets are posted to github?
In all of those cases, the person doing the upload does not "own" the content, nor did they choose the license.
There is no reasonable read of a ToS agreement that would allow Microsoft/Github extra rights to that content.