Dale,
"He related that these clips were some type of inside joke for Apple users???"
No. I don't think that was the reason.
I think they were included to help showcase iMovie's capabilities. Remember, this was a time when fewer people had miniDV cameras and those that did weren't accustomed to editing video on a computer.
Likewise, the first Mac I bought that had iTunes pre-installed also came with a sample music library. Again, I think to show people what iTunes was all about.
Matt