There are some devices like the Konke Temp/Humidity Sensor that ONLY work on channels 15, 20, and 23. (@aaiyar gets credit for finding this!)
And apparently the newer versions of this model don't seem to pair with HE at all. 
You have to be careful if using cheap devices like Tuya/Aqara or off-brand devices. For the non 3.0 stuff they should be on a separate hub as they don't play well with the other "good" Zigbee devices for some reason.
It's a total minefield out there unfortunately...
