That's the point. As a professor you're allowed to outsource the grading of written exams to you assistants (ongoing PhD teaching stuff). But you must do an oral exam personally.
> usually quicker for the well prepared students
That's true. More time is needed only in case the answer is missing and you have to check whether you hit accidentally the only poorly understood material piece or there are more troubles.
That's the point. As a professor you're allowed to outsource the grading of written exams to you assistants (ongoing PhD teaching stuff). But you must do an oral exam personally.
> usually quicker for the well prepared students
That's true. More time is needed only in case the answer is missing and you have to check whether you hit accidentally the only poorly understood material piece or there are more troubles.