Yes, this is still tradition among some German students. My 30y old brother has several scars („Schmiss“) from it.

I wonder if any graduate of a German university has ever run afoul of the various American state laws requiring candidates for public office to swear that they have never fought a duel.

I never heard of such laws in the US.

By definition, this is not considered a "duel", hence I think you could claim in good faith "no".

Wiki: Modern academic fencing, the Mensur, is neither a duel nor a sport. It is a traditional way of training and educating character and personality; thus, in a mensur bout, there is neither winner nor loser.