That's fair.
Here's the more specific post that deals with how primary/beacon channel selection is supposed to work:
Channels not available for 40MHz; 80MHz and 160MHz @ 5GHz - #104 by madsci1016
And in my usage with DFS channels, I've observed this to be correct. I can select any 20 MHz channel for a 40 or 80 MHz width, and OpenWrt uses that specific channel for the primary/beacon, and wraps it in whatever other channels make up the standard 40 or 80 MHz width.
But now I'm observing it not working with non-DFS channels, which baffles me. OpenWrt is ignoring my selection for the primary channel.