its SE's end. If this game didnt use SLI nore quad core.... well that would just be embarrassing =|
A lot of times, all that is required to get a game that doesn't use SLI/Crossfire on its own is to rename the game's executable to "crysis.exe" which suggests very strongly that support/no support is handled on the driver side. And since XIV is still only in alpha, I don't see nVidia or ATI rushing to update their drivers to include XIV. I remember back to the days when a driver was a driver and consideration for other applications was never part of the deal, but now if you go to the driver pages for ATI/nVidia you find that they do actually tweak their drivers for specific games/applications.
The XIV benchmark already makes use of multi-core CPUs. When I run the benchmark, I get activity on four cores. And I've read forum posts from people running the benchmark on SLI/Crossfire rigs saying that the second card was showing some activity, just not as much as you might hope in order to really maximize the benefit of the second card. That sounds like a driver tweak more than something SE needs to do on their end.
Regardless of whether it's an issue that SE has to address or something that needs to be handled driver side, to ship a game with hardware demands the likes of which we're seeing in the benchmark without SLI/Crossfire support would be a very substantial shortcoming for the game. It wouldn't surprise me to see a driver update later on in the beta that will cause a boost to performance for both ATI and nVidia cards (and especially nVidia, because the 4xx series is not performing on par with what it's capable of right now).