You are right, Glen, they are exclusive terms, and are left up to the hybridizer to declare ... bitone and reverse-bitone are just grouped together as a search term for the general type of color pattern (petals and sepals differing from each other). AHS registration instructions say:
"Bitone. The petals and sepals are the same color, but differ in shade or intensity. In a Bitone, the
petals are a darker shade than the sepals, i.e., rose pink while the sepals are pale pink."
"A Reverse Bitone has petals which are a lighter shade than the sepals."
And there is also: "Bicolor. The petals and sepals are of a totally different color, i.e., red and yellow with the sepals
being lighter in shade or color value. In a Reverse Bicolor, the sepals are the darker color and
the petals are lighter."
In the ATP database you can refine the search further to find just reverse-bitone, if you toggle the "flower form" button for bitones and put "reverse" in the color description search box. I don't know anyplace that can refine it to just bitone only, though.
