My child lost her firstname.lastname gmail/Google account for life for a one-time childish mistake. So, I guess you are mistaken.
It doesn't surprise me that your child could trigger accidentally one of those super ban. At least it's not that bad, they could have banned your account too.
I mean, I use Google products all the time. But I have multiple accounts ready to go, and everything important backed up offline, because I work in IT, and I've dealt with too many horror stories.
Google products work wonderfully until they don't, and the trigger to account loss may be a complete accident. And there is virtually no recourse when it does.
Their systems are not as foolproof as people seem to think. I've gotten other people's pictures in my photostream, and other people's appointments in my calendar. I'm sure it goes the other way, too, and that is something that 100% should be on your mind whenever you use their services.
Edit: To be clear, I would never blame them for wanting to stop a cascading explosion of emails. But I also wouldn't say it's impossible for a child to get an account banned.
"5.4 You agree that you will not engage in any activity that interferes with or disrupts the Services (or the servers and networks which are connected to the Services)."