They unconditionally say "You appear to be using Linux/Mac OS X/Microsoft Windows" regardless of what OS you are actually using. That's probably a vestige of a clever trick used along with autodetection on https://www.haskell.org/platform/ which does detect which OS you are using.
https://www.haskell.org/downloads/#platform links to installation options for Linux, OS X and Windows.
They unconditionally say "You appear to be using Linux/Mac OS X/Microsoft Windows" regardless of what OS you are actually using. That's probably a vestige of a clever trick used along with autodetection on https://www.haskell.org/platform/ which does detect which OS you are using.