It is happening everywhere. MS apparently makes no attempt to stop the folks selling keys on eBay or from dodgy websites, either. It almost seems that MS has resigned themselves to giving it away but doesn't want to officially announce it as long as there is any sort of revenue stream whatsoever that they can squeeze out of it.
The problem is that the whole license key idea is from the pre-Internet era. It didn't work well then and it absolutely doesn't work now.
Game and other software mostly moved on. Windows hasn't.
It's really difficult to design a license confirmation model that works on 3rd party offline systems. Windows is the only major OS that does this.
A key is just a key. It's not a license. Most of these dodgy sellers sell you a sequence of characters, nothing more. It just happens to pass the validation test - just like the keys you could find on forums.
You can even "mine" them.
Windows is just 15% of their revenue. Retail channel is probably few % of that, i.e. maybe ~1% of the total.
They just don't bother with tracking and blocking every illegal copy. It would cost more than they make from a legal one. It's better to lose a few million USD on stolen Windows and sell more Office / games / services etc.
Semi-sketchy, despite the sale going through PCWorld.
Asian sellers do this all the time: either advertising or selling via use a known "front" to sell keys. Just look what happens on techpowerup:
KeysWorlds, an international merchant of discounted genuine software, today unveiled Hot Summer deals on genuine software. Get stellar deals that help you get your new Summer and Back-to-School desktop or new notebook off the ground, with deals on Windows 10 + Office 2019 combos, over 50% off...
www.techpowerup.com
Keys advertised on TPU are obviously dodgy - probably coming from bulk licenses.
Those on PC World are probably the same, just camouflaged a bit better.
The question one should ask is: who sells these keys, really?
Article linked by OP mentions a "partner": Mediamart. There's no link or precise corporate info.
The only Mediamart I found is this:
https://mediamart.vn
The good part is that it looks like a proper store, selling hardware and having physical locations.
The bad part is... well, it's Vietnam:
Honestly, I just don't understand why people consciously give money to parties they don't know anything about, for a product that may or may not work.
What if I started selling Windows keys on the street? Would people pay $40?
That said, I'm also fully aware that people generally don't understand copyright and licenses.
Education systems just haven't caught up yet. General understanding of ownership is from XIX century at best.
I just ordered and paid extra for the disc. I far prefer having physical media.
You can make your own. Specifically: you can make a USB key, which is easier to use in modern PCs. Or you can reuse a DVD+RW for older ones.
What's the point in ordering one? That's just more garbage on the planet.