I'm pretty sure it's not a hardware limitation. The ATI (now AMD) chipsets didn't require this to support SLI and you can bet they certainly weren't using any NVIDIA parts along with their chipsets. Here's another quote from a different Anandtech article. Note that it specifically mentions a modified driver that made it work and not any additional hardware:
QUOTE
It appears that SLI will not be officially supported at this point although we have seen it running on one of the early boards with drivers that were modified but not provided or supported by NVIDIA. NVIDIA's answer to the X38 will be their upcoming MCP73 series that is targeting both AMD and Intel products. It appears the Intel variant will not launch until the fourth quarter with the AMD version launching in late Q3 according to our sources.
The MCP72 (and upcoming MCP73) is NVIDIA's southbridge. I don't see Intel licensing the X38 northbridge without one of the ICH9 variants to go with it (and we certaintly won't see dual southbridges).
This has actually been going on for years. NVIDIA has specifically blocked SLI on Intel chipsets in their driver for a long time. It's more matter of NVIDIA wanting Intel to pay for SLI licensing, and Intel not wanting to pay the fee. As a side note, SLI won't work on VIA or SiS chipsets for the same reason.
You are right though, there is a bunch of misinformation out there and it's hard to figure out what's right and what's not. I've always trusted Anandtech as a source (and they're always quick to point out when they were wrong, as well as providing updated information).