The "helping sell hardware without Windows" part is actually more like "helps PC vendors exploit a legal loophole and Microsoft keep its market share". They could just as easily install Ubuntu/whatever on computers that don't ship with Windows, but that might make some people stick with it and immediately install Windows on it. But if they put a useless OS like FreeDOS on there, they can check the "has OS" box, as well as the "no bundled license" box, without any risk to Microsoft's market dominance.
Hell, I think HP actually did put Linux on some of their laptops, but just as a compatibility layer to run FreeDOS, since they couldn't get it to work directly. This was clearly done for Microsoft's benefit and nobody else's - don't let anyone convince you otherwise.