Same in descent,states side..FL340, cleared to 16,000..Perfectly legal to set QNH ,but how often is the descent clearance amended,and how tired are we in that descent if it's the end of a transatlantic flight.
AIM and PANSOPS both stipulate that you change altimeter setting
at the TA in the climb and the TL in the descent. The PANSOPS exception is that QNH may be set above the TL when cleared for
approach and descent has begun. Eurocontrol say:
ICAO PANS-OPS1 requires that the altimeter pressure setting should be changed to the new reference when crossing the transition altitude/level.
7.2. Some national authorities stipulate that, when an aircraft has been cleared to climb from an altitude to a flight level, vertical position will be reported in terms of flight level unless intermediate altitude reports have been specifically requested by ATC. Similarly when a pilot is descending from a flight level to an altitude the pilot will change to the aerodrome QNH unless further flight level vacating reports have been requested by ATC, in which case the QNH will be set following the final flight level vacating report. https://www.skybrary.aero/bookshelf/books/142.pdf