Data point:
Two award tickets with different PNR. One passenger with TK Elite, the other with no status.
Tickets booked December 2021 directly with TK sales office.
Checked in exactly 24 hours in advance. Most seats were available for selection, almost nothing was selected/occupied at this early stage of check in.
Passenger with no status - TK automatically assigned seats and cannot change without paying additional fee.
Passenger with TK Elite - Free to choose any seat except for Emergency Exit Rows and Bassinet row.