Almost all of my breeding experience is with normals but I have seen strong tendencies for aggressive ball pythons to have aggressive offspring. I've seen this with two different lines through several generations.

Years ago when ball pythons where first becoming popular the main complaint about the species was that they where not good feeders. There was a common belief that more aggressive animals where better feeders and even better breeders. I have some great eating and breeding non aggressive ball pythons so I'm working to cull aggressive animals from my collection as I don't believe it's needed to improve ball python feeding. One of the things I like about ball pythons is their typical non aggressive personality. However, I could easily see someone who had worked with other more aggressive species not seeing aggressive ball pythons as a negative and perhaps even purposely breeding it into their morph projects. I don't have any inside info as to if that has actually happened or not but if aggression really is more common in morph ball pythons its one possible explanation.

It's also possible that aggression could be a side effect of some mutations. It's been proposed that in some species albinos can't see as well and this makes them more defensive. Maybe some other mutations cause chronic pain and a grumpy attitude.