Sort of? Like, the way it at least used to work, is that there was a MobileSafari.app that used the UIWebDocument class from UIKit.framework and which in turn used WebKit. I don't think anyone is expecting Apple to uninstall the UI widgets that are being used by numerous existing third-party applications, and yet it is still meaningful to be able to delete the Safari "app".

It's not. None of the UI is present in webview. Webview is just the 'rendering pane'.

No, it is not. Just create an app in Xcode and see that you have a WebView component. Easy to check: https://developer.apple.com/documentation/webkit/webview

Yes, (search) indeed they use WebKit [1] [2]. You also have the option to use WKWebView. But in this context you should use WKWebView if you want to access WebKit as a developer and be able to publish in the App Store. If you don't need to be accepted in the App Store you can use WebKit compiling it from the source.

[1] https://webkit.org/blog/15443/news-from-wwdc24-webkit-in-saf...

[2] https://developer.apple.com/documentation/webkit