My only guess is reading in a couple of places that OEM hardware manufacturers (Apple, Dell, HP, etc.) don't like people using reference drivers for their products. I don't know why that is, perhaps because they have one set of drivers that work when the product originally ships. Then they discourage driver updates, because they don't want to have people spend time helping people fix software problems?
The fact that their drivers are being "hidden" on ATI's domain space and not linked to from official web pages seems to at least support the generic explanation that manufacturers don't like people using reference drivers over custom drivers.
Either way, I'll be using the link I posted for any future updates, just changing the version number as they become official.