Screentime does not work when in Airplane Mode

Again, the Screentime passcode resides on the iPhone, not in iCloud, so whether Airplane is on or not makes no difference in changing the settings. If you have used a strong Screentime passcode that your son does not know then he cannot make changes to the settings.

If you want call AppleCare and ask to talk to someone about it. If this was true it would have been in every newspaper, trade magazine, and reputable website there is.

Thanks but I have no family to use it on. Call AppleCare. It would seem like it would only allow using items on the iPhone that do not use the internet which rules out server based games and some with in-app purchases. You certainly couldn't surf the net, etc. unless they turned WiFi back on. The post that you linked is from 2019 and didn't seem to stir up anything from anyone so I would reiterate, call AppleCare.

That was false even at the time it was posted which is why nobody responded. To reset the screen time settings they have to know the passcode.

I am too, I've never heard this. Do you have a link?