Possibly the supplier was talking of hardware failures.
The issue here (as it was several years ago with the re-known Seagate 7200.11 issue [0]) is not about the odds of multiple (hardware) failures together (which may actually be a very rare case), in these case it is essentially a software failure, a counter that crashes the on-disk operating system (if we can call it so) be it an overflow of the counter or hitting a certain value.
The chances of having almost simultaneous failures is near to certainty for drives that are booted the same number of times and have been powered for the same number of hours, if the affected counters are related to these events.
[0] Some reference:
https://msfn.org/board/topic/128807-the-solution-for-seagate...
>Root Cause
This condition was introduced by a firmware issue that sets the drive event log to an invalid location causing the drive to become inaccessible.
The firmware issue is that the end boundary of the event log circular buffer (320) was set incorrectly. During Event Log initialization, the boundary condition that defines the end of the Event Log is off by one. During power up, if the Event Log counter is at entry 320, or a multiple of (320 + x*256), and if a particular data pattern (dependent on the type of tester used during the drive manufacturing test process) had been present in the reserved-area system tracks when the drive's reserved-area file system was created during manufacturing, firmware will increment the Event Log pointer past the end of the event log data structure. This error is detected and results in an "Assert Failure", which causes the drive to hang as a failsafe measure. When the drive enters failsafe further update s to the counter become impossible and the condition will remain through subsequent power cycles. The problem only arises if a power cycle initialization occurs when the Event Log is at 320 or some multiple of 256 thereafter. Once a drive is in this state, there is no path to resolve/recover existing failed drives without Seagate technical intervention. For a drive to be susceptible to this issue, it must have both the firmware that contains the issue and have been tested through the specific manufacturing process.