Google Wifi - all ethernet connections show up as coming from router's IP

[DL6ER]

@mjmr89

DNS set to the rpi’s reserved IP as primary and google’s dns as secondary

Just a word of caution, please read

Primary vs. Secondary DNS

Following the regulations, there is nothing like a primary and secondary DNS server. These indications are quite misleading but many systems adopted it this way. We only list the DNS servers as primary and secondary, because this is what the providers write on their pages. The bad phrasing is supported especially by how Windows handles it. If you look at any Linux distribution, there is usually no separation between primary and secondary, but you can only provide a comma-separated list of DNS se…

@mjmr89

Not sure what else you may need to help that isn’t already in this message or the debug token, but please let me know if there is any other information I can provide.

Please check your clients that are connected through Ethernet if they show that they correctly received the Pi-hole's IP address through DHCP. I suspect that they are still list the router's IP address. The router is then doing the requests for them which causes its IP to be shows as the source.
I do agree that the fact that the WiFi devices are not affected by this is rather bizarre, so, before speculating more, I'd first like to see your response to what the wired (and maybe even the wireless!) devices received network configuration look like.