File this under possible bug, or perhaps something more interesting, but for those running Windows 10 build 10558, which leaked onto the internet yesterday, you may find the OS installing the Phone app from Windows 10 Mobile.
Indeed, we were tipped off about it and when checking our Store for an update Phone app build 1.9.30000.0 installed to our PC running the leaked beta OS.
Full story from the WindowsCentral blog...