LH had a very strict stance on not overbooking F but that's changing now during a trial period:

Revenue Management has identified some routes with very frequent changes by full fare ticket holders so that F is not sold at the optimal point.

For a trial period till the end of the year, LH will sell up to 10 seats up to a certain point before the flight, ensuring the highest number of paid for tickets at departure.

They are certain that their forecasts are so precise that they never have to offload or downgrade any passengers as 10 sold seats would go down to 8 due to the mentioned frequent changes.

In case there would be an actual overbooking situation very close to departure, Frankfurt would discretely reach out to some passengers and offer them some kind of deal in case they are willing to change their flights.

The change will increase revenue but will at the same time further minimize the changes of an upgrade with miles or an award ticket.