To be fair, you can't break the cold chain for foods, particularly dairy. Taking the yoghurt out of the galley and putting it back in gives no guarantee that it has been kept at the right temperature ready for putting back into the catering facility for a future flight.
Indeed that is correct. Pretty much the entire Club Kitchen, and certainly all dairy products, are thrown away at the end of every flight.
But just to reiterate, this is well below a 1% issue, judging from what I've seen and the experience of
CIHY. Not so good if you're in that group of affected passengers, but I'm wondering if there was some event that caused it, such as a last minute addition of passengers from another flight or some such.