I know all that. When I build a new machine I get an OEM disk from NewEgg or wherever. And I don't need the damn disk, all I need is the 25 digit license code. In fact, I usually build the system, install the OS from my generic MFST ISOs, make sure everything is working well, and then order the disk. You're given a few days before it has to be activated.
Again, this guy's situation has nothing to do with licenses. In this case, the guy is providing install media media for OEM machines with CoA codes affixed and intact. Those disks are needed to reinstall on a wiped hard drive or furbared Windows system. I do that all the time myself on machines that are brought to me for repair. No one has their install media (they quit providing it years ago). I use my generic ISO that matches what was installed by the OEM, do the install, then punch in the 25 code from the sticker, and off we go.
Except for Retail licenses, the OS license is locked to the hardware. Once it's activated on a certain platform, that same code won't activate on anything else. But the guy in question isn't transferring or selling or otherwise (re)distributing the license -- he's just providing people with (re)install media to use with their legit/legal licenses that are already locked to the hardware.