Why can't the first two texts in the main of the navigation.yaml file display children, and can only display chidren from the third

[lixianglong3210]

No description provided.

[lixianglong3210]

bad：
{
"text": "首页",
"type": "link",
"path": "index.html"
},
{
"text": "解决方案",
"type": "label",
"children": [
{
"text": "零售业或一般企业BI系统",
"type": "link",
"path": "article/解决方案/零售业或一般企业BI系统.html"
}
]
},

yes:
{
"text": "文档说明",
"type": "label"
},
{
"text": "首页",
"type": "link",
"path": "index.html"
},
{
"text": "解决方案",
"type": "label",
"children": [
{
"text": "零售业或一般企业BI系统",
"type": "link",
"path": "article/解决方案/零售业或一般企业BI系统.html"
}
]
},