I couldn't belive it - but it is seems to be true:
I suppose they want to keep the seats free for further cancellations and limit sales to the ones who really need and can afford to travel.
Source here in German:
Lufthansa streicht Flüge und Buchungsklassen - TRAVEL INSIDE (abouttravel.ch)
Google translate of the most relevant parts
Specifically, the booking class ban applies to all flights operated by Lufthansa (LH) within Germany and Europe as well as to the USA and Canada (westbound) as well as to all Air Dolomiti flights. According to the notification, only booking classes J and Y or additionally G and F (on USA and Canada flights) are available for these flights until July 31, 2022 (within Germany and Europe) or August 10, 2022 (to the USA and to Canada) available.
The reduced availability applies to all booking channels including lufthansa.com and the Lufthansa Service Center.
This means that only one of the available booking classes (J, Y, G, F) can be booked in each reservation system. In the case of Lufthansa flights, after flight cancellations, it is possible to transfer to the next higher booking class within the same compartment in accordance with the SKCHG/INVOL guidelines. This means: Economy Class passengers in Y class, Business Class passengers in J class