So the raid software thinks it knows better than the drive firmware, ignores the fact that it's operating a drive with no I/O timeouts, and helpfully times out the drive from the array because obviously it's not behaving 'correctly' in line with the unverified assumptions of the RAID software?

It reads to me like the fault here isn't just on the hard drive manufacturers, like everyone's made it appear in top-level comments of both issues about it this week. I'm glad I asked more questions so that I'm better informed to help my friends when they encounter this. I appreciate everyone in the thread offering help with the details.