GL-AR750S LuCi vs. UI WLAN "Auto" Frequency Setting

How come I can select “Auto” as a frequency for both WLANs in LuCi, but not in the UI? Is that because it’s not supported?

I’ve got it set and it seems to be working OK.

2.4G or 5G?

I think it works on 2.4G. Need to add this to the UI. But seems in openwrt auto just means channel 1.

5G there is a problem of DFS support so better not use Auto.

I was able to set both frequency bands to “Auto” via LuCi.

Can you elaborate on this? Is DFS widely used in the US (at least)?

ETA: “Auto” selected CH6 and CH36 for me today (and I’m in a very dense WiFi area) so it seems to work here OK.