You must be paired with your child's Smart Family Companion app to pause internet.
So if the child uninstalls the app (or disables it), then it stands to reason that there won't be any pairing, and I won't be able to actually "pause" anything.
Also quoting from the above page:
7. Turn your child's phone off and on again to put the limit into immediate effect.
So I have to have physical control of the phone in order to enforce the limit, but if I had the phone I wouldn't need the service now, would I?
By way of contrast, I can log into my router and immediately add or remove my child's MAC address from the list of allowed devices, and thereby prevent usage of the WiFi without needing access to my child's device in any way whatsoever.
So to echo what others have said, what is the value of a "service" that doesn't actually give you any effective control?