My understanding is that the KSP devs have experienced instability and bugs with the x64 builds for Windows/OSX which they attribute to Unity. In my experience

My understanding is that the KSP devs have experienced instability and bugs with the x64 builds for Windows/OSX which they attribute to Unity. In my experience (a few months out of date now) the x64 builds for Linux are not terribly stable, but perhaps the devs think they are more stable, or think that linux users are better equipped to deal with questionable stability and released that version despite the stability issues.