Issue of Private DNS nullifying router setting

I have setup the family filter of clean browsing on my router.

It blocks wonderfully.

However if a person enters security filter ip in the private DNS of the phone, it nullifies the family filter of the router and they can access porn.

Please tell me how to prevent this.

Extra details:

In my router I entered 185.228.168.168 as primary and 185.228.169.168 as secondary in the DHCP settings.

And I used DNS over TLS (security-filter-dns.cleanbrowsing.org) as a private DNS in my phone (Xiaomi redmi)

So please tell me how to stop android phone private DNS overriding router settings.

Thanks in advance