Microsoft are quietly merging Office code into their react-native-macos repo (github.com)

The commit in question, made on 16th July, uses the term "OfficeISS". I can find no mention of this online. Is this a straightforward code-name for their project to re-write their major apps in React, mentioned in the following tweet? https://twitter.com/TheLarkInn/status/1006746626617008128

I asked for clarification on how they were approaching macOS support in React Native, both:

1) in that Twitter thread (to no answer): https://twitter.com/LinguaBrowse/status/1006834843416657920

2) and in the subsequent Reddit discussion: https://www.reddit.com/r/programming/comments/8qqhlz/office_... (to an answer ignoring the macOS part of my question).

Microsoft are clearly going all-in on React Native:

1) TypeScript 3 has plenty of oddly React-specific features (e.g. defaultProps and PropTypes support): https://blogs.msdn.microsoft.com/typescript/2018/07/30/annou...

2) react-native-windows is thriving: https://github.com/Microsoft/react-native-windows

3) WinObjC is looking formidable: https://github.com/Microsoft/WinObjC

I think the future is bright for Microsoft, cross-platform development, and the React universe..!