Really? I'm interested in this because I've always thought it was the other way around.

Which model? Did Vaio later revert back something more conventional? As of 2007 Apple was using the same layout they have now and Vaio was using a fairly mundane PC laptop configuration. Side-by-side: http://www.notebookreview.com/assets/19478.jpg

Or is there some feature in particular that was copied that I'm not seeing?

Sony was using it in 2004 in this amazing notebook http://www.trustedreviews.com/laptops/review/2004/06/03/Sony...

Viao was using the case-between-the-keys style in the early 2000s.

Sony built the first portables for Apple.