Parental control: How to block personal hotspot?

Hi

Our kids can turn on their personal hotspot and use their phones as a access point for all non-IOS devices.

I have turn on parental control.

I set “Mobile data changes” to off

Still they can change this setting without pin.

Share with family members is also turned off.

ios 15.2.1 on all our phones.

parental phone: 11 pro max

Kids: 11

Is this a bug or do I not set this setting correct?