Is the iCloud Key-value independent for each device?

I am creating an app using iCloud with swift.

Save the characters entered in the Text Field named MyTextField to the iCloud key-value with the following code:

let vStore=NSUbiquitousKeyValueStore.default()
iflet str = MyTextField.text{
        vStore.set(str, forKey: "inputText")
        vStore.synchronize()
}

Also

let vStore=NSUbiquitousKeyValueStore.default()
iflet str = vStore.string(forKey: "inputText") {
    print("\"(str))
}

I did it in .

I saved it in iCloud without any problems in one iPhone, and I was able to read the values.
However, I installed the same app on two different iPhones and tried using the same Apple ID.
The key-value saved by one side cannot be read when the other reads it.
They all seem to behave independently.

Is the Key-value independent even if they use the same Apple ID but have the same Apple ID?
Please let me know if you know.