I also believe that black pastels and cinnamons are very different. They each have different pattern and color traits. I've seen what I'd call low quality cinnamons that look like a black pastel but if you have the eye for the pattern differences, they can be told apart.
Butter and Lesser.. That's harder to say what I think. Most butters I've seen look more "buttery" and are less likely to have spots or "eyes" inside the alien heads.. Also more silvery pixelation along the lower sides. Lessers are either more yellow, or more beige, and are more prone to having spots..
When I was breeding Lessers and butters, they, and their offspring were so entirely different looking that I could not have said they were the same gene.
It could be selective breeding, it could be different lines like pastels and how they look so different. For instance, lemons have thinner black markings, brighter yellow coloration, less blushing.. Blondes have tons of blushing in wider markings, flames, and a creamy blonde color.. I think lesser and butter is like that but the black pastel and cinnamon are just too different in too many ways for me to ever believe its that way with them.