Some good info there
Had a further look at the CEC issue, which I know for a fact doesn't work on certain cables, and came across the image on this page:
http://www.hdmi.org/installers/insidehdmicable.aspx
So my guess is some cheaper or older cables simply don't bother having the CEC part of the cable either save money or the HDMI spec back did not require it. If it was a spare pin on the connector until CEC came along, then I can see why they thought it was pointless to add that strand. It does show that HDMI cables can be different though.