They may or may not be deleted — the unified logging system has some complex logic for determining when log entries get purged — but you definitely don’t have access to them. The .currentProcessIdentifier scope means what it says: It gives you log entries for this process only.
If you’d like to see this improve in the future — it’d be nice if there were a ‘this app run by this user’ scope — I encourage you to file an enhancement request describing your requirements.
Seeing as iOS 16 just dropped I was wondering if you were aware if any such enhancement had been made in the latest update? Haven't got a chance to investigate this myself so posting here to allow the community to respond.