Right, that endpoint only has two selections, fiveGhzSettings and twoFourGhzSettings, nothing for 6ghz and nothing for the 2nd 5ghz radio. if you set the channel using that endpoint for 5ghz it sets it for the Lower band radio.
Here's the JSON:
{
"rfProfileId": "1234",
"twoFourGhzSettings": {
"channel": 11,
"targetPower": 21
},
"fiveGhzSettings": {
"channel": 149,
"channelWidth": 20,
"targetPower": 15
}
}