I understand, somewhat, what you and @Amethyst1 are saying, but at the same time they are selling this cable as supporting resolutions up to 3840 x 2160 @ 30Hz and Dual-link DVI to HDMI 1.4 as well as HDMI 1.4 to DVI.Maybe Dual link DVI is a spec that includes single link DVI - like how the HDMI 2.1 spec includes HDMI 2.0 so people can call HDMI 2.0 cables HDMI 2.1 even though HDMI 2.0 cables are limited to 18Gbps.
So this cable is compatible with dual link DVI - you can connect it to a dual link DVI connector or cable, but it can't transmit dual link DVI - only single link.
HDMI uses the same pins and signals as single link DVI so there's no converter chip and the cable is bidirectional. HDMI is just single link DVI with a new connector. If there was a converter chip then the cable would cost more than $12 and it wouldn't be bidirectional.
Club 3D has a product page for this cable that says the same thing and a support forum, so if it doesn't work it's going to be them just flat out lying about what it supports and I'm only out $12.
Anyway, I got my Radeon 9600 Mac/PC card and it has no issues in my 733Mhz QS or my 867 Mhz QS.
I tested the X3 has no issues in a QS 733/ QS 800/ QS 867. All three report Keylargo V3 and UniNorth 1.5 v1. As we already know, but I'll just repeat it, the X3 has no issue in my MDD Dual 867Mhz or my G5 1.6Ghz. So whatever the stepping issue is, it doesn't effect any of my tests. Sadly I fried my Dual 1 Ghz QS, so I can't test that.