Why do we even set the DNS servers on the rooftop WISP radio?

On my rooftop WISP radio, the DNS Servers are set to the typical Google Servers 8.8.8.8, and 4.2.2.2

However, I have been testing for DNS leaks at

and I definitely have a DNS leak even when I'm on VPN!

In testing, I noticed that both my home wifi router & the rooftop WISP radio had the same two DNS Servers set up, so, I changed the two servers on the home broadband router to a set that I found here:

What I noticed is that the DNS server used was never the DNS servers set up in the rooftop WISP radio!

The DNS servers that show up in the tests at

and at were ONLY the DNS servers set up in the home broadband wifi router.

Given that the home broadband router is "winning", I tried to put an incorrect DNS in my home broadband router, to see if the rooftop radio DNS settings would act as a "failsafe".

Nope.

I was *assuming* that the rooftop radio's DNS servers would win.

But, the rooftop radio's DNS servers never kicked in and I temporarily lost my ability to ping by domain name when I put in a bad set of DNS servers in the home wifi router.

What is going on?

Specifically, why would the rooftop radio even *have* a setting for the DNS servers if the setting is never used?