[smartmontools-support] Unusual degree of variation in "Extended self-test routine recommended polling time"?

[Dan Lukes]

James Masterson wrote:
> I recently received a batch of 6 brand new HGST He8 drives and when running
> an initial long self-test on them, I noticed that the extended self-test
> routine recommended polling time exhibit a very large degree of
> variability.

> Device Model:     HGST HUH728080ALN600
> Extended self-test routine recommended polling time: (1367) minutes.
> Extended self-test routine recommended polling time: (1217) minutes.
> Extended self-test routine recommended polling time: (1242) minutes.
> Extended self-test routine recommended polling time: (1133) minutes.
> Extended self-test routine recommended polling time: (1167) minutes.
> Extended self-test routine recommended polling time: (1083) minutes.

I never seen variability of such kind on WD and Seagate models.

Different firmware versions ?
A bug in smartctl itself ?

Note that it's defined as recommended polling time, not the length of 
extended self-test, thus the time disclosed is based on an unknown logic 
preferred by vendor ...

Dan