Don't understand the problem. "Any DX9 card with 512mb of VRAM will run it". Seems pretty straightforward.
(It's the 512 that makes my old system no good..... I've run all the previous games quite well with a "crap" card. An underclocked, mobile, HD 2600XT w/256mb vram. It was enough to get low-mid settings out of Oblivion, Fallout 3, and FO:NV. So when they say that any 512mb DX9 card is good enough, I believe it. Yeah, there might be one or two old GPU models out there with 512mb and a weaker chip, but they'd have to be pretty rare.)
There is a separate thread better suited for defining differences between what is or isn't CRAP. If Intel produced it, that's basic crap for video. If it was produced for business it was named / numbered 100, 200, 300, 400, and 05, 10, 15, 20. Makes no difference if it has a GB of attached RAM, it's not good enough to use more than 128 because of its 64-bit bandwidth. Game-capable graphics are 600s and upward, with the "Enthusiast" Level taking over at 800 and upward. For Geforces, the numbers don't count as much as the prefixes: GTS means game-capable, and GTX means either the upper end of gaming, or High End enthusiast.
There are also some "budget" cards priced below actual game cards, and numbered HD 5570, HD 6570, GT 220, GT 440.
Game-capable cards will have 128 bit memory systems that work most of the time with 256 MBs of RAM, but also fairly often, but not constantly, with 512 MBs. No matter how much you attach, the Low End won't reach even 256 MBs' worth of VRAM. Depending on the core speed and RAM speed, the budget cards won't use 512 MBs at all often. The middle of the range will access that much "often", and the upper end of the range will be fast enough to deal with 512 MBs frequently. If that's what Bethesda means, then they should have SAID so.
Enthusiast cards start out being 256 bit memory cards, which start out always able to run 512 MBs, and very frequently able to go on up to a full GB of VRAM, but it's the combination of performance features involved that make them powerful and expensive, not just that they may have quite a lot of RAM attached.