I suspect that fired triggers still poll
While I don't know diddly squat about scripting in ofp, I do know programming techniques and languages reasonably well.
The triggers would be intitally 'registered' by the engine.
The engine builds a dynamic queue in a frame event handler.
If an author can interrogate *a* specific trigger to find out if it's fired, then that status will be part of the trigger, rarely, part of the queue, and the answer therefore would be that the engine still polls the trigger to find out it doesn't have to do anything! (just like the author can)
If you can't interrogate 'this' (type of) status, it's because the trigger has been removed from the queue (but not deleted)
The clue, programming wise, to the answer is whether you can address a trigger by a 'this' style inference (queue) or only by specific name (a deregistered trigger). Btw, I don't know what 'this' means in ofp, just educated guessing.
OFF TOPIC
@Mac, I know your reading this thread and are a busy man, so may have missed my returns on the editorupgradeONE.pbo, would you mind looking at it please in the relevant thread.