The project is marked as proposed, suggesting Microsoft is still working on the OS. Its area path of OS/Core/SiGMA/ also makes sense given its close relation to Core OS. According to the Reddit user, the entry appeared to be for a code change in Windows to address an issue.
The leak comes just a few weeks after Microsoft Language packs were spotted on the Store for Andromeda. At this point, we can be almost certain the company is still actively developing the OS, though its release date is still very uncertain.
For the unfamiliar, Andromeda OS is Microsoft's modular approach to Windows. It will give it flexibility across a number of different devices. For example, Microsoft could place Windows on a smartwatch, but only with the components necessary for a wearable device.
More importantly, though, it'll be a big step towards the unification Microsoft has been searching for. Though desktop, Xbox, and Windows mobile all use Windows 10, the UX is slightly different. The change would allow some much-needed consistency while also making it easier for developers.
The previous teardown of language packs contain references to calling and left and right screens. It lines up with rumors of Microsoft's flagship Andromeda OS device, which is thought to be a foldable.
A previously leaked roadmap pointed to a 2018 launch for this device, so it's possible we'll find out very soon. Microsoft is no stranger to delays though, and considering previous reports suggested the device would pivot to a laptop. Given those rumors, a 2019 launch may be more realistic.