My neighbor moves around his channels, too. That’s what’s making me comment that it’s likely more common than we think. I’m not at home to prove this and I’m getting downvoted for sharing, but I’ve watched him move between 36, 40, and 44 at a frequency that suggests it is happening automatically, probably when all of his sessions go idle or something. I have observed this with multiple tools.
My 5 GHz was on 44 this morning, because I happened to look for unrelated reasons. I just SSH’d home and it’s now on 36 without interaction from me. Specifications are not implementations. I’m almost positive this is a common feature which I’ve seen in many APs over the years, even though it’s not per-packet like Bluetooth (which I was also aware of, given that I'm experimenting with a Bluetooth 5 mesh system for IIoT).
As far as I know it's not dynamic, though. It just happens when a device connects to a base station and only "steers" the client to connect using one of the 2.4 or 5 GHz bands, and that doesn't interfere with channel selection.
The AP also has a function to scan bands to find the "best" channel to use but that disconnects all devices while the scan is in progress. I think some APs might be doing this automatically (?). My other AP (a Mikrotik) has an "auto" channel selector but I don't know what it does or when.