GET /tasks responses are not stable

First I do a GET /tasks, and I get among others these three tasks in this order:

• nightly1679472131
• 1679472123
• 1679469983

Later I do GET /tasks, and I get after the task nightly1679472131 a bunch of new tasks that hadn't appeared before, like:

• 1679469458
• 1679469602
• 1679471838
• 1679472126
  (you can check this is true by doing GET /tasks now).

These appear correctly after the nightly, because their started_on time is before the nightly and the tasks appear in reverse chronological order. But the question here is:

If these tasks started_on before the nightly, then why did they not appear in the first request?

The problem is that if new tasks appear in the middle of the tasks list, I might miss them completely. I must know up to what point I should check the tasks list.