I believe he was joking. Saying that an OS like that would never catch on.
Your right though, the first few of Linus' posts are cool, but I don't think that that is the first one. Goto www.li.org/linuxhistory.php
and look at their history for a whole list of the posts. There is one where he says he is doing something which is:
just a hobby, won't be big and professional like gnu
For someone so clever to be so wrong...