This answer describes a scenario where if a sin (relations with a non Jew for purposes of marriage) is committed without witnesses, one gets punished with kares, but if there are witnesses he gets only lashes.
This seems strange since
It goes against the generally established paradigm that the presence of witnesses results in equal or more severe punishment. Examples : desecration of Shabbos w/o witnesses = kares, with witnesses = capital punishment. For virtually every transgression, the presence of witnesses and warning enables an earthly court to take action, but it does not lessen the punishment!
Not only is the punishment lessened quantitatively, but also qualitatively : Kares implies death and possibly also loss of world to come, while after lashes the transgressor continues to live and still has his world to come. Such a qualitatively significant reduction in punishment simply because there were witnesses who witnessed the crime (which ought to make it worse, not better), seems to run counter to how this works for other sins.
Is there something missing here?