As a general comment, there are pros and cons regarding splitting the two wifi bands vs having them use the same SSID.
With the latest devices, and band steering, having the same SSID should make things simple and optimal - with the router and/or device choosing the best band for the location within the property.
However, some devices don't like a single SSID and therefore splitting the two bands, assigning a different network name (SSID) to each addresses a number of problems.
'Boosters' can present particular challenges as to which choice to use, and their functionality with/without the bands split.
It can be a case of try and see as there's no hard and fast rule - it depends on your unique situation with devices and environment.
There are a number of articles online including this one
Interesting observation regarding the Hub 4 and 5GHz from the OP - I would suggest trying with different devices and the latest drivers if possible to see if it's still the same situation.
------------------------------------------------------------------------------------------------------------------------------
I know a bit about Wi-Fi, Telecoms, and TV as I used to do it for a living but I'm not perfect so don't beat me up... If you make things you make mistakes!