PS Ident is not required for DM purposes because departures from the LTMA auto DM.
Not all the time, they don't. As I recall AUTO DM is at the bottom of 9020D / HCS's "to do" list. Hence it's possible to get airborne without the flight being activated, particualrly if the P time is wildly inaccurate.
Not always obvious to TC either of course. In BYPASS the squawk would convert anyway.
Result. LTMA deps can arrive on AC sectors with NO warning, no strips and as BACKGROUND or RSE raw tracks (not always easy to spot, particularly if you aren't looking for/ expecting them)
rgds BEX