It's most likely obsolete since it's from "core 2" era when north bridge(including pci-e host controller) was still on the motherboard and not integrated. Note that since "core i" era there's no nvidia chips onboard anymore to support SLI.
EDIT: there ain't any mITX boards on the certified list since you can't usually fit two cards into one slot
Ah that makes sense. There is more recent tool called differentSLI: https://github.com/EmberVulpix/DifferentSLIAuto
But presumably this would just be needed if you're trying to SLI a GTX 970 with a GTX 960 or something? Or maybe two different brands of the same model.
Ha, and yes, that does make sense why they wouldn't usually be certified
EDIT: Well anyways, maybe in 2016 I'll be using an A4 with 2 GTX 1070 pascal mini's or something