Apple "just uses LLVM" in the same way Apple "just uses Webkit".
Apple hired Chris Lattner back in 2005, just as he completed his PhD. At the time, LLVM could just barely compile Qt4[0] (the result didn't quite actually work yet) and was still hosted on CVS.
Lattner had to make LLVM production-ready (rather than a research project), add a bunch of major features, start a C/C++/ObjC frontend (Clang) and create a team of LLVM developers in the company.
Apple shipped their first bits of LLVM-based tooling in Leopard in 2007.
[0] https://web.archive.org/web/20111004073001/http://lists.trol...
Calling it "Apple's" threw me off too, but it's not entirely misleading because without Apple, it might not have become a production-ready compiler. At the least, I would say Apple did more than "just use it".
1.) GCC was designed for command line use, not to provide integration (for instance, debugging info) into a modern IDE.
2.) Objective-C was not a priority for those who maintained GCC, but was for Apple.
Debugging info works similarly in all compilers (GCC, MSVC etc) - it's saved in the compiler output and read by the tools like IDEs.
It's equally weird to describe Android as "Google's".
Same applies to LLVM. The only reason it might not seem a fair comparison is that Apple has run LLVM as a truly open source endeavour, whereas Android (which marketed itself to geeks as the more open platform) has, as you rightly point out, been run as a closed-source project with occasional begrudging nods to its ever-shrinking open source subset.