Testing with the Xiaomi AX3200 / Redmi AX6S with 23.05.0, I just discovered that channel scan does not work if the router is configured with a DFS channel. See example below:
5Ghz radio configured in channel 100: channel scan does not work, shows only router's own signal:
5Ghz radio configured in channel 36: channel scan does work as expected:
So as @slh mentioned above, this seems to be a known limitation.