why wechat（微信） can do this? APNS push can Wake up parent App in background?

Question

Why WeChat can use PUSH Notification to activate the application in background ？Even activate active the application which closed by user?

I know WeChat use Notification Service，but it can not active parent App in background！

So，WeChat can unlimited use Silent Push?

I try to use Silent Push+Alert+Notification Service, I can active app in background.

I did it In Debug Mode!(Maybe Debug Mode is Different）

But According to Apple regulations， Silent Push can not be used frequently！

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Here is My Payload

payload = {
        "aps": {
            "mutable-content": 1,
            "alert": {
                "title": "Nice To Meet U",
                "body": "推送服务测试"
            },
            "sound": "call_ring.m4a",
            "content-available": "1"
        }
    }