Correct setup for using rDNS?

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Recently switched from running two PiHoles to two AdGuard Home servers.
In PiHole I manually added all hosts assigned to static IP's for hostname resolution, not ideal, but it worked.

For AGH I see I can add Persistent clients for the same result. I also see AGH can do rDNS, but my Firewalla box doesn't respond to AGH as it automatically turns off DNS Booster to my DNS servers that are listed for my LAN/VLAN's

To circumvent this, I added a third AGH server that my first two AGH servers point to and it provides rDNS resolution. I believe this works as Firewalla doesn't disable DNS Booster for this server.

My question is, is this a valid configuration or am I introducing unnecessary complexity to my network by setting it up this way?