The fall 2019 operating system updates for Mac, iPhone, iPad, Apple Watch, and Apple TV are staggered all over the place.

Generally, Apple releases its big fall operating system updates at nearly the same time. We get the new iOS, tvOS, and watchOS all on the same day (or nearly so), and the new macOS within a week or two. Yes, there are further “point releases” to add features and fix bugs, but the big drop is often more or less at once.
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https://www.macworld.com/article/3438541/apple-ios13-ipados13-macoscatalina-watchos6-applearcade-appletv-release-schedule.html