Flutter controls all the actual pixels, recreating the iOS and Material styles in Flutter code. React Native describes its view contents in JavaScript, but uses native Java/Cocoa APIs to draw the actual pixels.
Flash/AIR and desktop Java are other well-known technologies that controlled how the actual pixels were drawn. If you wanted a native-looking UI, you had to mimic one in framework code.
React lead Tom Occhino pointed this out at the React Native launch. With the React Native approach, your app matches the iOS N+1 style when the user upgrades. With the Flutter/Flash approach, your app matches N+1 when you upgrade your version of Flutter and push a new release.
Flash/AIR and desktop Java are other well-known technologies that controlled how the actual pixels were drawn. If you wanted a native-looking UI, you had to mimic one in framework code.
React lead Tom Occhino pointed this out at the React Native launch. With the React Native approach, your app matches the iOS N+1 style when the user upgrades. With the Flutter/Flash approach, your app matches N+1 when you upgrade your version of Flutter and push a new release.