More likely that is people selling old technet keys. That was a problem before Microsoft changed their technet policy. People would sign up for $199, then get several dozen Windows and Office keys. Sell them online, then subscribe again with a different email address.
These are (or purport to be) the packaged 3-user family packs that come on a physical box with a CD. I have one, in fact, but mine was given to me by a friend who bought it with a Toshiba notebook that he promptly corrupted with multiple viruses, got frustrated, and switched to a Macbook. The copy I have came from the Geek Squad guys and seems to be legitimate -- I have installed it on one additional computer with no problems. But Office is now up to version 2016, and I expect 2019 will be out soon. It stretches credibility that there are still legitimate, unsold copies of the Office 2010 family pack still out there in the wild.
TL:DR -- this isn't a key card download, this is the package with physical media and an activation key on the package.