Lithium batteries age even just sitting on the shelf. I fly RC planes and we store our batteries at 3.8V to lengthen their life, but they still deteriorate even when not used. Like anything else, I guess.
I suspect the RC plane batteries you've been using for five years are not the same chemically as the EV car batteries in use in the UK for five years.
As I mentioned, the article specifically mentions that the battery chemistry has been changed and improved.
It neglects to dive into the chemical engineering specifics of such changes, as would be expected for press such as the WSJ.
I dare say there is as much variation in the attributes of the LiPo/Li-Ion battery family as there is within the borosilicate glass or soda–lime glass families (ie heaps).
The fact that the article states that this appears to result in longer life and the fact that you talk about your RC plane batteries not having a longer life would suggest that the fine specifics of the two batteries may well differ.
They've been sitting unused, in their original packaging, never opened... They're still sitting at the charge they shipped at, but the capacity is so diminished that one can't even run an esp32 for a day. I've tried cycling them to see if I can get the capacity back up, but I think they're toast already.