Aflatoxin kills the Phoenix, but the death effect of creating a Malignant Cell is overridden by the Phoenix ability.
Skull Buckler kills the Phoenix, but the Phoenix ability is overridden by the death effect of creating a Skeleton.
The specific descriptions of the Aflatoxin and Skull Buckler effects are:
"Poison the target creature. If the target creature dies, it turns into a malignant cell."
"Attacking creatures have a small chance to die and turn into skeletons."
The descriptions lead me to believe they should behave the same way, and it bothers me that they are inconsistent. Since neither of them lobotomizes, I would prefer the Phoenix ability to override the Skull Buckler, but I just want to know if anyone else is bothered by this. I don't think it's important to change, and it could just be one of those quirks of the game you have to just know, but I don't really see why they aren't consistent.