IPv6 configuration not working

I need to configure NextDNS with its IPv6 addresses from my dashboard for my Android phone, but NextDNS gives me this warning message:

This device is using NextDNS with no configuration, make sure you set the configuration ID shown below in the app settings

Since IPv6 does NOT require IP updates like IPv4 does, what's the point of this warning?

Does it have anything to do with the fact that my ISP would have to offer IPv6 for it to work, something my mobile ISP doesn't currently offer?
Or is my reasoning completely irrelevant, and are there other issues that need to be addressed?

P.S. I would like to inform you that I use NextDNS through the "personalDNSfilter" app, by creating a local VPN and not changing Android's private DNS.