VueJS：通过this。$ children访问子组件与组件对象有什么区别

Question

为什么单击更改消息按钮时子组件数据属性未更改（由于此语句store.data().msg = "New Message (Changed)"）

<template>
    <div class="wrapper">
        <p>{{msg }}</p>
        <button @click="changeMsg"> Change Message</button>
        <store ref="myStore" />   
    </div>
</template>

<script>
    import store from './store.vue'

    export default {
        data: function() {
            return {
                msg: store.data().msg
            }
        },
        components: {
            store
        },
        methods:{
            changeMsg(){
                // console.log(this.$children[0].$data.msg);
                // console.log(this.$refs.myStore.msg);
                store.data().msg = "New Message (Changed)"
            }
        },
        mounted() {
            console.log("App: mounted called");
        },
        updated() {
            console.log("App: updated called");
        },
    }
</script>

此外，我想知道使用对象console.log(store)与console.log(this.$children[0])来访问子组件之间有什么区别