The game is indeed 32 bit, but is configured to take advantage of up to 4 GB of RAM (normally 32 bit apps are limited to 2 GB of RAM). However, this feature only works to the full extent if you are running 64 bit version of Windows.
That's why devs strongly recommend 64 bit Windows even though the game is formally 32 bit.
BTW, to put it simple WOFF.exe is responsible for main screen, menus, settings, etc, while the "flying" part of the game is CFS3.exe. It is still 32 bit of course.