That may be so (and I'm not an Apple insider, although I do know a few LLVM devs). I guess you could say a driving motivator to find an alternative solution to GCC was to not be reliant on a GPLv3 license. Traditionally I don't think the license has stopped Apple from contributing a lot back to the OSS community (just look at WebKit).

Besides, a compiler is just a compiler. Maybe someday down the road they will start producing their own ISA, but until then even if they're making their own ARM chips it's really hard to get it to do special Mac/iPad-only magic.

What I do know is that Clang was funded by Apple almost from the start, it was engineered right from the start to be more than just a compiler but something you could plug into the IDE as well (as the latest XCode demonstrates, it has completely unbeatable C insight).

LLVM itself is also far more extensible than GCC, just look at the slew of new-ish (last 3-4 years) of projects that have launched using LLVM. Have you heard of any such projects being launched with GCC? I can't think of any (maybe if they did, they weren't proud of it).