Why guess? This is data that is almost certainly aggregated back to the manufacturer and could be available as a published report. The fact you don't see this report I think is indicative of the reality.
> Pessimism about battery longevity is giving us all cheaper second-hand EVs
The seller sets the price. Not the buyer. You should ask why the seller is willing to let the vehicle go for a lower than expected price for a given number of miles.
> had lost just 15% of their capacity, on average
There are no average batteries. The used vehicle market doesn't work on averages, it generally works on worst cases, particularly in an as-is (no warranty) sale.
> in other words, there was no active cooling of the battery
As it requires a four way valve. That's a common failure point in EVs.
> Many manufacturers provide long warranties for their batteries
Do those often persist through private party sales?
I'm not trying to be mean, I think EVs are great, but hybrids are still obviously better, and the market is far more complex than this author would like to acknowledge. I dislike articles that start with a conclusion and then spend pages trying to justify it. The data to actually answer this question was available but completely unused here. I did not find this convincing or informative.
Think of it this way. There is a segment of the buying market that is hostile to these vehicles by default. Waving your hands with no data to back it up only makes it worse.
Anyways..