In the end, it’s statistics, yes. Maybe, a Mac running a windows VM could produce similar output, or somebody could run Linux, copy over the specific fonts from Windows 8, tweak font rendering to match Windows (e.g. in when to use type hints), fiddle with line spacing and page width until their LibreOffice or abiword produces the same line breaks and spacing, etc, but that somebody would try to do that is quite unlikely to start with and also may be very hard to accomplish (and that’s something experts could have tried to do. If so, they could testify about the difficulty of pulling it off)

⇒ I don’t think it’s fair to call this speculation, let alone pure speculation.