That is terrible, and completely unsubstantiated advice. It's no wonder you are an EX microsoft dev, if in fact you actually are. I suspect however that you are not since you are not aware that Microsoft has no need to issue a key of any kind. They can simply extend a digital entitlement to anybody with a registered Microsoft account, any time they wish. No key needed. If you had ever worked for Microsoft, you would be aware of that.
Plainly, I'm calling BS on everything you've said here and in several other threads as well. Unless you can show us some facts to the contrary, that's how it's going to stand too.
And further, the suggestion that it's a good idea, or that somebody should be open to buying pirated keys is not only fundamentally unsound and wrong, it's also against our rules. Even beyond that, I've personally communicated with people in key positions in Microsoft and as I've communicated to our staff and other moderation members, the final word from Microsoft is that they do not EVER, EVER, sell licenses or keys through ANY of the retail channels themselves except for the Microsoft store, and they do not EVER authorize ANY of their authorized retailers to sell them below common retail pricing structures. No valid keys that are approved for sale by Microsoft will ever find it's way onto one of these gray sites.
They might not all get blacklisted, but anybody selling keys ~20 dollars or more below average retail has either stolen them, is selling previously used keys or has absconded with them from a list of those included with a bulk OEM purchase, which is the same as stealing them.
Microsoft has flatly answered my inquiries with the direct statement that any key sold on sites like Kinguin, CDkeys, digital-racks, G2A and similar "gray" sites is NOT being sold by an authorized reseller and if it is not being sold by an authorized reseller then it is not valid and will more likely than not get blacklisted at some future point. The only, ONLY reason, most of these have not had this happen yet, and a lot of them have, is that Microsoft simply wanted to get everybody hooked into and onto Windows 10 first, for their own reasons such as the data mining they have done though that platform, but at some point there is likely to be a mass blacklisting. Even if there isn't, it is still in the interest of everybody who buys or uses Microsoft products, and expects them to support those products, to see any money for said products going into Microsoft for development and operating costs, and to maintain shareholder profits, rather than going into the pockets of scammers and mafia operations who are generally the ones that are involved with the mass theft of product keys.
Anything beyond that, I'll leave up to somebody else to smack this entire notion down with.