confirmed inasmuch as: EFAX appear to be SMR whilst EFRX are “CMR” (conventional)

Best not to use “PMR” as a term for the older drives - SMR (shingling) is an extension on top of PMR technology and I just had a WD regional marketing manager latch onto “PMR” to claim “the drives are PMR” and therefore there isn’t an issue.

The concensus is that in this particular instance the issue is rotten firmware and there’s no good reason why the drives should be returning these codes

I’m also getting feedback that it’s difficult-to-impossible to rebuild RAID5/RAID6 arrays using EFAX drives, not just RAIDZ/Z2/Z3 arrays.

It’s not just WD pulling this silliness. Examples have been cited of disguised DM-SMR units from SG too (eg: ST3000DM-007 and some Ironwolf models have been confirmed)

I’ve sent a heads-up to the smartmontools developer list to let them know what’s going on. Hopefully ways will be quickly developed to flag disguised DM-SMR drives

Just to add more fun: TDMR (Two Dimensional Magnetic Recording) is a way of describing the zoning and block reassigning(indirection) functions necessary in a SMR drive and you essentially can’t have one without the other - there’s no need for this functionality in a CMR drive. That means the implications for issues are intertwined if you see drives described using either SMR or TDMR.