I don't think it's a sign of Apple taking security seriously as much as it is a lawyer avoiding liability suits.
I think any competent PR representative would have inevitably pulled those statements, as they were never true even when they were written.
> The Mac is designed with built-in technologies that provide > protection against malicious software and security threats > right out of the box. However, since no system can be 100 > percent immune from every threat, antivirus software may > offer additional protection.
Something similar is still present in today's security page: http://www.apple.com/osx/what-is/security.html (near the bottom)
[0]: http://web.archive.org/web/20100123154433/http://www.apple.c...