When a model is generated with OntoUML stereotypes, an objectified fact type appears as a class connected to its participants, but the relationship that is derived from it is not generated at all, and neither is the link stating that it is derived.

That derivation link is what distinguishes an objectified relationship from an ordinary association class: it says that the relationship holds between the participants because the objectified relationship exists. It is also what makes the cardinalities unambiguous, because the constraints can then be stated on the objectified relationship rather than on the derived one.

Expected: with OntoUML output enabled, the derived relationship between the participants is generated together with a derivation link to the objectified relationship. Preferably switchable, since on a diagram it adds lines while for exchange formats it is the point of the exercise.