It seems you're not aware of the fact that Asus redesigned their site a year or two ago and started "mass-correlating" FAQ entries across multiple motherboards inaccurately. For example I've found non-UEFI boards with FAQ entries talking about UEFI. It means nothing. You're welcome to contact them and inform them of the mistake.
If you really don't believe what I'm telling you, then please find a tool that will provide a full PCI descriptor dump of all devices on the PCI bus. One such tool for Windows is RWEverything
. Launch it and make sure the PCI sub-window is visible, then find the icon at the top of that window which is labelled "Resource Summary" and copy/paste the results here in a code block. After that, I'll find you the exact Intel PDF documents which reference the PCI Device and Vendor ID of the relevant ICH7 southbridge chip that's on your motherboard.
It's either going to turn out to be the stock/base ICH7, which lacks AHCI -- or one of the sub-models which does support AHCI where Asus intentionally chose not to make use of the AHCI option ROM capability when designing the motherboard. You're welcome to contact them and discuss the matter further, but AFAIK Asus hasn't invented a time machine that would allow them to go back to 2005/2006 and re-engineer already-released products.
Furthermore, the ICH7 was engineered back in 2005 and was a somewhat "transitional" southbridge -- it was the the first to provide an option ROM that offered AHCI (on specific sub-models). With the release of the ICH8 and onward, inclusion of AHCI and its option ROM became more and more common universally. The ICH7 is known for being a "sore spot" in this regard -- it comes up on the FreeBSD lists on occasion, because even some server motherboard manufacturers chose to use the stock/base ICH7 rather than the sub-models that supported AHCI, and buyers blindly assumed their board would have such support. Bzzt.--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.