No, that means that it's very, very difficult to RE the feature in question- and if they had the info, it'd probably be a different story.
I'm not having a go at the Mesa developers. The problem is just that there is a crucial piece of HyperZ missing that prevents it from working properly, so that many "bugs" can be fixed simply by turning HyperZ off.
And without intervention from ATI, this is not going to change, so it's a bit galling for an ATI representative to sing the praises of the Open Source drivers.
It looks like there are only two device IDs in use, however, so it's pretty hard for the driver to accurately identify which variant is running and put up the proper name. I don't think it matters, though, since the BIOS is different for each system and the driver navigates the BIOS to find which clocks, features, and outputs to use.
I did a bit more digging and found that we seem to have stopped using the X12xx names in favour of "690" (desktop) and "690M" (mobile), so having two device IDs is correct after all.