Yes, the Leaf uses passive battery cooling as opposed to Tesla and others with active cooling. Their first-gen battery chemistry was also worse in hot climates. The newer battery is a different chemistry that has held up better.
Alternatively, it could be used a state of charge tracking mechanism that conceals battery degradation. Say the battery has 100KWh, but the remaining energy gauge reads zero after 80KWh are expended. You could be degraded to 90KWh but you wouldn't perceive any reduced usable energy until it degrades below 80KWh.
Yes, and my point is that the mechanisms to prevent battery degradation can often end up masking the degradation. This isn't nefarious, it's the byproduct of good state if charge management.
I have a 2015 Leaf with 45k miles on it. Battery state of health is 90% according to Leafspy. I’m in the SF Bay Area. Maybe it’s because of the more temperate climate here, but we’ve just had zero battery degradation problems.
My gut feeling is temperature and constant deep discharging probably explain most of the issues with Leafs. Like a lot of things there is a curve with a knee and it's easy to drive a leaf so you're on the wrong side of it.
I don't really know how Leafs batteries are connected but one could also expect that a smaller battery pack has less redundancy. If due to bad luck a couple of cells go bad you lose a lot of capacity. More likely to happen the less redundancy you have.
I would call Leaf's cooling system as "body contact passive cooling". Calling it as "air cooling" is harmful. Proper air cooling with A/C should be significantly better for health.