shannon's right about the history. You can see an Osborne "super hypo" on the classifieds today, in fact: it's a beautiful hypo variant but not the ultra-light kind of thing that we're discussing here. That's why, as shannon says, the issue was discussed here, alternatives considered, and since the visual effect is that the animal is extremely light, or that there's an extreme reduction in melanin (compared to regular hypos) that the term "extreme hypo" both distinguished them from steve's AND was descriptive, always a good thing in naming.
But right now it simply describes a look. We don't know yet how the genetics work--again, as shannon says, is it a new morph? or an extreme end of a range of possibilities from "regular" hypos? mike alvarez bred a pair of extremes (from mike falcon) this summer and one of the six babies, at least, was not an extreme imho, i saw them in person. Maybe a different male was put with the female uninenttionally once and forgotten and fathered the non-extreme baby; or maybe extreme is not a simple recessive.
It's just a fact that there's more we DON'T kbnow right now than we do know. So more breedings, more speculation, more observation, more discussion. I'm sure we'll figure it out sooner or later. It would be very nice if it turned out to be a simple recessive, but....
peace
terry