When playing Disco's Evil Santa Boss Fight and died it occurred to me that the death message I got back was "ilxMine was knocked from a high place and got finished off by entity.SmallFireball.name". So the death message showed the java entity name because it is probably not defined well.
It is hard to reproduce but I made a small contraption to let you see how it works. (See attachment). In the world is also a small explanation of how I did it.
I think it's easy to fix.
My theory:
In the previous versions you just burned to death, the fireball did no damage. Now in this version the fireball does damage and they forgot to translate the class name into human languages.
How to fix:
Just add "entity.SmallFireball.name=Fireball" into the "minecraft.jar/lang/en_US.lang" file (if using another language add it to that langage's file). Oh yeah, don't forget to remove the META-INF folder... (silly java and its checksums)