From what I've read, the issue is that the reduced performance has a direct effect on stability: When used as part of a RAID array then these disks can exhibit

From what I've read, the issue is that the reduced performance has a direct effect on stability: When used as part of a RAID array then these disks can exhibit unexpected long pauses under load, which causes the RAID controller to mark them as faulty and kick them out of the array. There are quite a few stories of people being unable to use these HDDs for archival, for this reason.