I think it means, that the Amiga was tied up to the artistic scene BEFORE the Mac was. Not that the Amiga was released before the Mac. When released, the Mac had nothing to do with digital art, video, music and that sort of stuff, like it is today. It was more sort of a home or office solution, later delving into DTP.
(that's why I always wanted to have a mac when young, to me it was the natural "philosophical sucessor" to the Amiga)
aAhh how I loved computer Chronicles, but I watched it from 1994 and ahead. Let's check out this episode.