Indeed not, however Fluka does. Its because Fluka does not perform a robust check for being on a boundary when starting a source particle. In MCNP we must specify which surface the source starts on, this is not the case for Fluka. The user must ensure that the source does not start on a surface. 

In our case it is also called when a particle is not located within any volume. I agree that it should not be the case that we need such a method.