Nitpicking ;-)
Very good analogy, Raoul - it often seems as if this Habitable Zone surrounds a variable star, or perhaps even a periodic nova. And of course, the hotter the star, the "bluer" its spectrum - meaning, when things get really hot, the UV component might make a zone uninhabitable, even at a safe distance for temperature.
I know that rotating fluids - such as protostellar clouds - form discs, and that even a captured object with a high orbital inclination will be "perturbed" toward the average ecliptic, given enough time. But, in the strictest of technical senses - as Dyson pointed out - a star's habitable zone is a sphere, not a torus.