It's not really the energy restrictions that cause the problems (except for the one useless mode, which is an Energy Star-related issue).
It's that you can't illuminate a plasma with a full-white screen to the same level you can for a partial white screen. The amount of current it would take is just out there and would require far beefier power supplies and electronics and the longevity of the whole display would still probably be too low to be really acceptable for a CE product.
There is no difference in HDMI cables. If you can see the picture without visible dropouts or sparklies, the cable is working at 100%. No other cable will display a better version of that picture. You're simply wrong if you think there is a better digital cable than one that is already working.