Middleware framework extension

[kirillbashtenko]

Hi, can you plz help me to understand how this works?
https://modernjs.dev/en/configure/app/server/enable-framework-ext.html
My understanding is that we can use express or koa as middleware and their types, but after enabling this flag I still see that in Middleware we receive this type:

export type MiddlewareContext<T extends 'worker' | 'node' = 'node'> =
  HookContext & {
    response: ModernResponse & { locals: Record<string, any> };
    source: {
      req: T extends 'worker' ? Request : IncomingMessage;
      res: T extends 'worker' ? ModernResponse : ServerResponse;
    };
  };

Thanks in advance