I can't believe it's the same iso file for x86

Looking on the web site, I saw that it was suggested to download
the same .iso file to try open-darwin on a x86 processor.

How could the same .iso file be used both on G3-like processors, and
i386?

I thought that maybe it use fat-binaries that contains code for both
platforms, but they have very different boot procedures, so how is
it possible?

--Paul