Hi, I think you have an error in your logic. You mention that you check that ashift for the pool is set to 12, but ashift is not a pool wide setting. That is you can create a pool with a single vdev initially and set ashift 12, but you can then add additional vdevs later and they will only have ashift 12 if they are detected to have 4k sectors (ie default would be ashift 9).
cheers Andy.