I'm absolutely having the same problem. Just got the Xfinity XB8. Same problem.
As soon as I got the gateway home and hooked up I, of course, start playing with settings. Just on the mobile app at first. I see the option to split bands or "Let Xfinity's super duper gateway decide for you how to connect to your devices" yeah. . . PASS! so I turn it off, and notice that the 2.4G and 5G security settings are the same but the 6G isn't. Furthermore the 6G cannot be changed. While at the same time only my M2 MacBook could even see the 6G network. I do my due diligence.
🧐 "Does my iphone 14 pro max have a WiFi 6 antenna?" ✅ Sure does!
As a test, I turned all of the security setting s for the three networks to WPA3- Personal to be the same as the 6G. Still nothing form the 6G to my phone
VPN is definitely not the problem either, wife and I have the exact same phone, hers has never had a VPN, mine does. Still nothing.
Also, changed security settings in the phone manually setting up the connection to include IPv4 and IPv6 addresses, adding DNS information. Nope.
Going into the router and manually adding my phones MAC address to try and initiate a connection from the router side. Absolutely nothing works.
The only thing I can see, that I am unable to change but may (*just may) have something to do with it is that when you get to the Edit screen in the router for the settings of each individual network it has a locked "Channel" each one (2.4, 5, 6) being different.
If you go into Gateway > Connection > Xfinity Network and scroll down the only bonded channel is 44, which I think must be the channel for when you let them bridge all the networks together and decide for you what you can use.
If the default Channels could be changed in that page and the channels in each network bonded to match, it would possibly be smooth.
IDK, I'm trying to figure it out too.
Also, I have no wifi pods, just the gateway and client devices.