This isn't to dispute your assertion, but I think things are still quite a bit different. A lot of things provided by Foundation on macOS are still not available in Linux's Foundation, nor CoreFoundation, so one has to defer to something like Glibc — which, then again, is not available to the static Linux distro. On Windows, it's useful to use WinSDK to do things that Foundation would normally do.
There's all sorts of little things that Swift on non-Apple platforms just don't have yet. Little footguns because the Swift rewrite of Foundation isn't quite equivalent yet.
It is getting close though, which was my point. Honestly I got bit recently by DateComponentFormatter that does not exists on Linux, but it’s been a while since I’ve had things like that. We even have (NS)AttributedStrings (including the NS version, which I did not expect…). Of course no fonts and co, but that’s AppKit/UIKit/SwiftUI, so it’s normal.
