While it is correct that only the local Aviation Authority has the power
to ground aircraft it would be extremely unwise to ignore a safety
warning from the manufacturer.

The tech note and advice from Schemmp Hirth was correctly represented -
the factory say these aircraft must not be flown until inspected. If you
are affected by a factory defect, you might get some credit when it
comes to repair. If you (or your bereaved spouse) are the proud owner of
a pile of composite confetti, you may find the factory and your
insurance company less helpful.