The scrollToTop key is used when you want the page in the nested routes to start at the top before it is rendered. By default, Nuxt scrolls to the top when you go to another page, but on the child pages in the nested routes, Nuxt stays at the same scroll position from the previous child route. So, if you want to tell Nuxt to scroll to the top for these pages, then set scrollToTop to true, as follows:
// pages/users/_id.vue
export default {
scrollToTop: true
}