In fact, the genus Cinnamomum which contains cassia and ceylon (C. cassia and C. verum, respectively) is pretty large and diverse. Sometimes what people refer to as cassia can actually be one of several species, e.g. C. burmannii, which is also often referred to as korintje. There are others that can be ambiguously named. E.g. the aromatic compound camphor is harvested from camphorwood (Cinnamomum camphora), which is not to be confused with the tree known as camphorwood in Australia, Cinnamomum oliveri.

I have no real point here other than cinnamon (i.e. the genus Cinnamomum) is fascinating and confusing in equal measures and people should definitely read up on it.