I wouldn't go with WD Purple or other surveillance-class drives for gaming due to the nature of these drives. You may encounter problems with corrupted files or slower read speed as these drives give priority to the sequential writing tasks over everything else. These drives do work with quite low noise and temperature levels but are not recommended for regular usage outside surveillance and video recording/streaming.
Based on WD's own marketing, they should be no worse than the Reds. If it is, how about linking to a data sheet that describes how the failure mode will be worse than a Red, when not using ATA streaming features? It may have a slightly worse chance of corruption while writing during a power failure,
if it write-caches more than other drives
without using streaming, but that's not normally a big worry, for a data-only desktop drive.
If you're going to tell us they should only be used for
X, how about some documentation, preferably with some meat to it, about
how they are more likely to fail when used differently, or how they will significantly under-perform when used differently.
IoW, can you explain
why it's not recommended for regular use,
based on feature implementation or specific design decisions, rather vague marketing?
NAS drives can work but it would be a waste as regular type of usage such as gaming doesn't really need hte NAS features in those drives.
So they should have aggressive power saving, that can get annoying really quick, instead, with a Blue (AKA Green)? Or, have a whiny thing that practically can't be made inaudible, like a typical Black? Only getting 100-150MBps sequential is a small price to pay for it being always ready if spun up, and not going, "eeeeeeeee, rat-at-at-tat-at, eeeeeeeeeeee," all the time.
You can try to color it however you like, but a single model could do all of it as well or better, from the perspective of a power use (most necessary features have existed for some time, and streaming is optional, if more recent),
except that market segmentation is useful for controlling prices, and it's easy to sort of shame companies into not using the "wrong" drives. So, we have to choose what features are more important to us, when purchasing, rather than being able to configure basic power settings to accomplish the same task, which would allow for much easier choices (much older Hitachis, Seagates, and Samsungs, allowed exactly this, with their AAM settings, though it often took booting into a different OS, if running Windows). FI, there's no technical reason Reds or Purples should have TLER hard-coded in them (years ago, some drives would just honor the command); there's no reason any number of software-configured power settings couldn't make the Green and large Blue drives more tolerable for intermittent desktop use (even right from within Windows, and assuming they'll still be 5xxx RPM); and so on.