路由器存储无法识别路由器参数

我们有以下路由方案:

export const ROUTES: Routes = [
  {
    path: ':userId',
    component: fromContainers.OrganizationComponent,
    canActivate: [],
    children: [
      { path: '', pathMatch: 'full', redirectTo: 'posts' },
      {
        path: 'posts',
        loadChildren: './views/posts/posts.module#PostsModule'
      }
    ]
  }
];

userId 这样,但是当我们移除 children 用户ID

http://localhost:4200/user/r1RORssFG --> WORKS
http://localhost:4200/user/r1RORssFG/posts --> DOES NOT WORK

这种行为背后的原因是什么?