Consider the following example:

extension type ET(Future<void> value) implements Future<void> {}

class SomeClass implements String {
  const SomeClass();
}

enum SomeEnum { first }

both enum and class have contextual info when hovering over their name (e.g. that it's a class and implements String):

for extension types this tooltip has only the name:

Please complete the following information:

Dart Code extension: 3.82.0

App: Visual Studio Code
App Host: desktop
Version: mac 1.86.2

Workspace type: Dart (LSP)

Dart (3.3.0): /Users/incendial/Desktop/flutter/bin/cache/dart-sdk
Flutter (3.19.1): /Users/incendial/Desktop/flutter (No device)