Fair enough I might have gone too far with the speculation, we don't really know.
For the record I wasn't saying that that engines built today would support DX9 (actually I said the opposite) but that if they used an existing engine that has been around for a while it would have likely supported DX9.
RE small companies making their own engines I don't completely agree, it's too broad a statement. The kind of engine we are seeing here is quite complex to build from scratch and is a big undertaking. I doubt many small companies, specially with relatively little resources, would opt to do that. If you are referring to other scenarios of simpler engines, or their own game engines based on existing 3D graphics engines then I can understand that but is that what happened here?
Heck, even CCP took Unreal 3 for their upcoming DUST thing. They tried to build their own engine for the world of darkness game and Walking in Stations in EVE (theres speculation they were beta testing the technology in EVE which angered people) and that has since fallen through. They themselves said they were overreaching doing all that an their company is (well was before the 20% layoffs) 600 ppl strong.