Why isn't Xfinity XB8 optimizing 2.4 and 5 Ghz channel use?

Trying to understand why I'm experiencing more wireless disconnects on my home network lately, particularly noticeable with some Apple Airplay2 based music streaming from a PC connecting to the 5 Ghz network.

It turns out that my neighbor's 5 Ghz wireless signal is stronger in my home office than my own signal and is using the same channel (157).  When I looked to change the configuration on my XB8 to use a different 5 Ghz channel, I couldn't find any options to change the configuration.  But I did find this link re: XB6 and newer Xfinity gateways:

https://www.xfinity.com/support/articles/change-wifi-mode-admin-tool-xfinity-xfi

• Most of these gateways have been upgraded with software that manages advanced WiFi settings automatically to help optimize your home network and provide the best performance possible.

If that's true, then why is my neighbor's configuration using the same 2.4 and 5 Ghz channels as mine when there are other unused subchannels?  I don't see that any optimization is happening at all.  From the nearly identical channel configuration of his network, I'd say he's also an Xfinity customer running the same equipment.

Already hugely disappointed that my xFi pod ethernet ports seem to be capped at 50 Mbps, and now I see that the XB8 modem/WAP is apparently too crippled to make better use of available spectrum.   I note that other customers have experienced similar issues and over a year later Xfinity has done nothing to provide customers with the tools to resolve this issue short of buying their own equipment.