13.0 is not just a marketing number. It is the number stamped in the binaries produced with the Ventura SDK. It is the number in Ventura SystemVersion.plist. It is number used in the availability markup in the headers provided by the Ventura SDK. It is the number you use for runtime version checks when you use `#available` in Swift or `@available` in Objective-C. You will not find 10.18 in any of those build or runtime contexts (or anywhere else) because it is not the version number of macOS Ventura.