The TL;DR problem: Why does the 6GHz channel create a separate Wi-Fi Network (SSID) that I have to connect to, isolated from my main 5GHz/2.4GHz network? This strips you of the entire point of having a mesh system, which is that it determines and transmits the best signal to you based on where in the house you are. The 6GHz band should be one of 3 bands included under the same SSID and the mesh system should determine which access point and band best suits my device at any given moment.
So I just bought the brand new (as of April 2022) tri-band XE75 system (AXE5300 at Costco). The XE75 and AXE5300 are identical, but XE75 comes with 2 devices and AXE5300 comes from Costco with 3. It is TP-link's 1st WiFi 6E capable router. It looks and functions very similarly to the x68 that came before it. It has a 2.4GHz channel, a 5GHz channel, and the brand new 6GHz channel (the x68 had a 2nd 5GHz channel for dedicated backhaul instead of a 6GHz one). The XE75/AXE5300 allows you to decide if you want to keep the 6GHz channel as a dedicated backhaul channel (keeps the signal between mesh devices strong) or use it as a 3rd band for your devices that function with WiFi 6E (like the Samsung Galaxy S21 that I have and newer devices).
HOWEVER.. when you select the option to use the 6GHz band as part of your Wi-Fi network for Wi-Fi 6E capable devices (I know there are few), it forces you to create a separate Network Name (SSID) that you have to connect to separate from your main wireless network.
-This means that the entire point of a mesh system now disappears as the router will no longer determine for me if I will have faster streaming speeds using the 5 or 2.4 GHz bands because I'm too far from (or have too many obstructions of) the 6GHz signal. It will just keep me on 6GHz until I'm out of range of the signal then would potentially connect me to the other main Wi-Fi network. That generally doesn't happen, so instead, I sit with 2-3 bars of wifi signal and a mesh system that is unable to adapt.
-Another problem that this creates is you are then unable to Chromecast to other devices on your network since you're on a different network.
--Another problem I realized today is that when I leave the house and return, my phone reconnects to my non-6GHz SSID (probably because 5GHz/2.4GHz signal is stronger at range) instead of the 6GHz SSID since I had logged into both (it has happened 3/3 times since installation). The solution I created was turning off the auto-reconnect feature of my non-6GHz SSID in my phone's Wi-Fi settings.. but yet another reason why having all one SSID would be best.
At the end of the day, it is a poor implementation of Wi-Fi 6E. I don't know if they just didn't have time before release to fine-tune the system that decides when 6GHz should take over vs other bands.. but I would at least like to know that this is being worked on and will be brought to the device in a future firmware update. If not, I may just return this system before my 3-month window with Costco runs out.