When using a balanced antenna such as a half wave dipole, with an unbalanced feed line such as coax, an RF choke can be used to block RF current emitted by the transmitter from splitting up at the antenna feed point and traveling along the antenna and also down the outside of the coax. Without the choke, the outer shield of the coax becomes a radiating part of the antenna, which is usually not desirable.
Why do amateur radio operators refer to the RF choke in this instance as a balun?
To me it seems that the RF choke isn't a balun and doesn't convert an unbalanced transmission line to a balanced system at all, but rather just removes one of the effects of connecting an unbalanced transmission line to a balanced antenna, that being the unwanted current traveling on the outside of the shield of the coax, by blocking it.
Isn't a real balun for example a ferrite ring with wires arranged such that common mode current is cancelled out in the same way that a transmission line operates while at the same time allowing differential mode current to pass?