[agsnu]

It's not just the WebKit bit, basically the entire app implementation is actually shipped as a "Private Framework" which lives outside the .app bundle. e.g. on macOS % otool -L /Applications/Safari.app/Contents/MacOS/Safari /Applications/Safari.app/Contents/MacOS/Safari: /System/Library/PrivateFrameworks/Safari.framework/Versions/A/Safari (compatibility version 528.0.0, current version 623.1.14) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1356.0.0)

There's a bunch of other private frameworks (SafariCore.framework, SafariFoundation.framework, SafariPlatformSupport.framework, SafariShared.framework, SafariSharedUI.framework, SafariSwift.framework) as well. I haven't checked but I assume it's similar on iOS.