Configure AT&T ARRIS BGW210-700 with EAX80 AX6000 WiFi Range Extender

AT&T seems oblivious to the fact that it says mesh in their router. If I mention Netgear, they simply say "We do not support third part equipment." I asked what mesh equipment they do support, they point to their sales site. I point out that none of them say they are mesh. End of the conversation. Seems that getting two peices of gear to work together properly is unsupported. 

As for speed and being on the same channel, I'm not seeing an issue. I've done tests. I'll disable WiFi on the AT&T Gate Way and walk around my house testing speeds. Then I do the reverse, turn off the Netgear and enable the AT&T WiFi and re-test speeds. Speeds follow distance from the router. 

With both WiFi's on, speeds seem to hang on to the WiFi that it happened to connect to when the WiFi device was powered on. When I walk to the opposit WiFi, it seems to hang onto the remote WiFi for a couple speed tests and then switch. It is not quick like I would expect for a true mesh, but it does seem to switch. I do not know a way to know for sure that it has switched. I've used WiFi analysers. I can see the two APs on the same channel. I can see the relative strengths of them as I move about the house. I cannot tell which one my device connects to. I can only make assumptions based upon speed tests at different distances from the two APs. 

Thanks for your input. It is helpful to have other opinions other than only my own.