I think endo/ecto are mechanisms and homeo/poikilo are results. They mostly match up (why spend all that energy generating body heat if you're not going to use it to maintain a constant maximally-biochemically-effective temperature?) but not 100%. An ectothermic-homeothermic animal would have to put more effort into using the environment to maintain a constant body temperature. Google says there are some lizards in that category.

I guess the distinction would be that hot and cold are quantitative. There are "cold" blooded reptiles that love temps well in excess of 120 degrees.