Why there is no separate Mac app
There is a version of this that ships a native Mac app, charges for it again, and drifts out of sync with the iPhone one within two releases. Apple silicon makes that pointless: the ARM binary you already bought runs on the Mac unmodified, widget extension included.
What you give up is nothing at runtime — the widgets are local, they work offline, and they do not care whether your phone is nearby. What you give up is the Mac-native window chrome: opening the app itself shows a phone-shaped window, because that is what it is.
Settings do not travel automatically between the two installs, though. The Mac copy keeps its own cities and formats, which is usually what you want — a desk clock and a pocket clock rarely need the same time zone.