I take your point about the very low probability of this happening, this is of course correct. Not everyone is on yet another F flight, however - in some cases we could be talking about people on a very infrequent F flight that was only made possible after a lot of Avios collecting and card spending. It's easy to see why people may be concerned in that situation, justifiably or otherwise.
You make a fair point, and I'm not trying to have (much) of a go at
Gorcat here. The issue is that some people and some websites have irresponsibly set a mood music about this, and yes FT has some clear examples of where downgrades have happened. Now I (and others) can give reassurance, I guess, but am I feeding the beast, or indeed feeding the troll? While we ponder that, here is the good news thread to go alongside:
No problems with a 2-4-1
(and any recent updates to this would of course be good).