Maybe dividing the drives roughly in "higher than average variability" and "low variability" and then looking at the AFR for this subset can show some relation. Of course as the AFR for many drives is already quite low, the effect might be too small to distinguish from noise.
On the topic of temperatures: Have you run an analysis whether a drive increasing in temperature (or maybe even decreasing) compared to its base line and "neighbors" results in a higher chance of failure?
I'd be interested if you have data to compare similar drives with stable tempretures against diurnal tempreture cycling.
I'd imagine you have fairly constant data centre type environments though which would confound analysis for such questions.