It's been quite a discussion, WD offering a NAS series that in hindsight, isn't RAID compatible because they are shingled magnetic recording drives.

Shingled media recording (SMR) disk drives take advantage of disk write tracks being wider than read tracks to partially overlap write tracks and so enable more tracks to be written to a disk platter. This means more data can be stored on a shingled disk than an ordinary drive. However, SMR drives are not intended for random write IO use cases because the write performance is much slower than with a non-SMR drive. Therefore they are not recommended for NAS use cases featuring significant random write workloads.

WD now has released a clear overview to create some clarity. Western Digital on the topic:

The past week has been eventful, to say the least. As a team, it was important that we listened carefully and understood your feedback about our WD Red NAS drives, specifically how we communicated which recording technologies are used. Your concerns were heard loud and clear. Here is that list of our client internal HDDs available through the channel: