Or the only difference of those specialized SKUs is a single parameter in the firmware making a different tradeoff for, lets say, random seek vs. sustained sequential reads/writes. A different cache strategy. Or whatever.
Being able to charge $100 more for that is very worthwhile.
2014-2017 I worked for HGST, just as it was being assimilated by WD.
There were definite hardware differences between drive categories back then, and as well as the firmware adjustments, there would be things such as additional accelerometers to detect and help protect against shock (eg: portable drives), higher quality bearings and head/head mechanism differences.
But, or course, that was then and I can't speak for now.
IIRC the main difference for WD was how it reacts to errors. Consumer drives will spend minutes to retry rw operations. Surveillance drives will mostly ignore errors as it's more important to have some footage than none. And NAS drives will immediately report the errors.
I think the "larger NAS" drives have better shock absorption, which is a hardware thing.
No matter what, it's a reason why you can't get any large capacity drive at Best Buy. They'd have room for one SKU but can't afford to stock an Amazonian variety of unusual types. I feel the whole industry has gone in a bad direction.
My workstation has a modern case that doesn't really have a lot of room in it for HDDs, so I added an external HDD for my sports photographs. I sure as hell don't get the bit about "serious external HDDs have their own power supply" because it is one more thing that can fail (get unplugged) and cause data loss. I'd get warmer and fuzzier feelings if the drive was powered off USB.
People have been battle testing those cheap as possible external drives on top of hot xboxs in enclosed cabinets for years and years now. Backup, and I would think failure rates would be too small to consider.
I'm mostly concerned about the power cord getting unplugged if, say, somebody is vacuuming around the area. On top of the usual "whole machine gets turned off" failure mode that happens maybe 10-20x a year in my neighborhood because of power loss there is a "machine is turned on but HDD is powered off" case.
Personally I don't trust a NAS as far as I can throw it, or rather I'd use one the way I use Amazon S3.
My home server has a ZFS array, the media server and some other programs access it directly. If I want to move files to or from it I use SFTP. If I want to back files up to it I use rsync. I have Lightroom running pretty good on an external HDD, no way I'd take my chances running it on a NAS.
An appliance with the primary role of storage, and the ability to share files over the network are the distinguishing features for a NAS. Network support for iSCSI, SMB, NFS makes a NAS; sharing data exclusively over the media protocols (http, rtsp, etc) makes it a media server
By "NAS" most people mean "box they bought from someone to share files on a network" - think Qnap or Synology. They'll call a "NAS" that is home-built a server, even if they do basically the same thing.
To make it more fun, you'll have people refer to "I don't have a NAS, I run FreeNAS on my server."
Being able to charge $100 more for that is very worthwhile.