That's only the case in the first write. Rewritten blocks suffer from severe write amplification in SMR drives due to much larger segments needing to be written even for small changes.

Rather than ideal, a rebuild is actually the worst case scenario as the RAID may detect the drive as unresponsive as it scrambles to catch up and thus gets dropped, exacerbating the problem for the other drives in the array. This is HL2 Resonance Cascade bad.

If it is software raid (like ZFS or Btrfs), the writes are random. Plus, it's not clear SMR can be made to accept heavy write load even when the load was predictable.

The iX systems blog linked above implies that:

- not all SMR drives seem to cause problems

- rebuilding on a non-fresh/cleard hard drive can have negative performance implications due to how SMR works

So my guess is that it's a problem with the firmware which can potentially be fixed. After which they could be used in a NAS, just aren't necessary as far as you might think. So I guess it's probably not looking too good for the lawsuites chances to cause much yield/discount.