It sounds like you have a reading comprehension problem?
> And as far as the "career track" aspect goes, have them keep coding part of the time and keep calling them a programmer.
1) You're missing the part where the majority of programmers don't want to be doc writers, aren't qualified to be doc writers, and aren't good at being doc writers.
2) It's not as simple as having them "keep coding part of the time", because the standards for hiring a coder are different from the standards of hiring a doc writer. Apple wouldn't necessarily hire the same person to do both. It could be a rare situation where Apple would consider the same person to be good enough for both jobs. This is like saying of an American football team, "Why not just have the quarterback play defense part of the time?"
Remember, the point of this is to produce high quality docs. Quality over quantity. Apple is already churning out low quality docs.