I think you're right about "platform independence", in the sense of the term as you use it here. I should have probably elaborated on other ways I use the term.
First, some 3rd-party SW providers do have to support multiple databases, OS'es, etc. I once worked on a product line that supported customers using Oracle, SQLServer, and DB2, running on WinNT, Solaris, and AIX. That isn't an issue for everyone, of course.
The other, more subjective aspect of portability is the way it contributes to SW quality. Loose coupling and abstraction have been hallmarks of good software for decades. However, while doing this usually yields better, more flexible software, you often pay a price in performance (e.g., going through abstraction layers and not exploiting specific optimizations), as well as the extra effort to write "abstractly". The Architect has to make the appropriate tradeoffs.
Anyway, I agree with you that it's risky for Sun to over emphasize platform neutrality, especially in server-side SW.