Three days is, agreed, too short. A week is just about possible, though...
I've seen a blog-post, authored a bug in Radar, assigned it to myself, and fixed it the same day. Whether it goes out in the next release is more a decision for the bug-review-board, but since the engineering manager (that would have been me) sits on that too, it's just a matter of timing and seeing if I can argue the case.
To be fair, the closer we are to a release, the less likely a change is to be accepted unless you can really sweet-talk the rest of the BRB, and there's usually a week of baking before the actual release goes out, but that has sometimes been shrunk for developer-preview releases...
The fixing of a bug at Apple is the easy and quick part. It's the submission process from then until it gets released as part of an OS update that is the ridiculously long (and too often difficult) part.
The submission process is pretty trivial too - as long as your code gets a PR review, and is given the green light to be merged into trunk (which is the 99% case, even if there are PR comments to address), it's going to be in the next daily build.
The releases are the things that are few and far between - generally though, a nominated daily-build (based on the pre-determined release schedule) is triaged and tested by QA and engineering for a while before release, and then ... it's out there...
...Unless something goes unexpectedly wrong with the nomination, anyway. That's pretty rare because builds are constantly being made, regressions identified, and new bugs discovered and earmarked as "must-fix" (or whatever) on a daily basis. B&I have a fairly good feel for how things are going at any given time.
It's really just timing. If you can squeeze another fix in before the cutoff deadline for the nominated build, you're in. If not, you wait until the next one, which can be a while...
Yeah, that was not at all my experience in CoreOS/SWE, where we would sometimes/often have to wait weeks for submissions to turn around in B&I to become part of "daily" builds. Glad you don't have to put up with the same ridiculous crap process.