I think the editor further muddies the water when he writes [RadCom, Feb 2022, p.65, 1st paragraph] “If you are in a far-flung part of the UK, or further, or operating in the early hours there is no need for a regimented move to another frequency as you are unlikely to be interfering with others that might want to make use of that frequency”.
This is yet another interpretation and adds a time-of-day and location factor as to whether to treat that frequency as a CC/CF or a COA. This furthers my belief that the [once clear?] distinction between a CF and a COA is gone forever – a pity.
I note however that the 2m FM CF (145.500) - in the UK at least - is very widely treated as a calling frequency (probably helped by its popular use) and for example the 80m QRP CW COA (3.560) is treated as a centre of activity.
It seems the recent changes to band plans reassigning CFs as COAs, and the widely different interpretations as to what that means, hasn’t helped.