"Timing starts upon skipping the initial mission cutscene, and ends when the mission has been passed."

IL rules

᠌
There is no problem with determining the timing start. If I understand the rules correctly, this is NEXT FRAME OR MILLISECOND either after the disappearance of mission name on the black screen, or after interrupting the initial cutscene (because speedrunners usually don't wait for the end of the initial cutscene)

BUT.

᠌
"Timing ... ends when the mission has been passed."

IL rules

᠌
The EXACT MOMENT, which is the end of the mission, IS NOT INDICATED HERE. Is this the frame or millisecond when the message "mission passed!" appears? Or is it a moment earlier when the HUD appears again after the final cutscene? Or some other option?

᠌
Earlier, before "The IL Situation", the end timing was the appearance of "mission passed!". Proof:

At 0:25 and after you can read:

"Timing ends when you see Mission passed"

᠌
In summary, a request to the moderators - accurately and clearly specify mission end timing in ILs

In that quarry 7 IL by Akzo that you showed, I think mods considered the in-game time which the one mission provided.
If you check the video, you'll see that the mission takes place between [COPS 08:00] and [COPS 04:31] so it basically makes 03:29.

You misunderstood meaning of my video proof, Mehmet. I just wanted to demonstrate the timing rules for individual levels before “The IL Situation”

For Quarry levels, Pilot School levels, races, etc. we use IGT

While I'm talking about other missions, such as "555 We Tip", "A Home In The Hills", "Against All Odds" etc., missions where we use REAL TIME

᠌
The problem is that "timing ... ends when the mission has been passed." from the current IL rules rules sounds too vague and inaccurate

It's not vague. The mission passes when the onmission flag is set to 0 by the mission end. The usual way to determine this is by looking at the icons on the minimap (when they reappear at the end of the mission, then the mission has been passed). So far this hasn't been an issue, and even if someone's run had no other missions remaining, other methods could be used to determine when the mission specifically ends, like at the end of a cutscene or something. In cases where being on the mission while onmission=0 is part of the strat for the IL, the same thing can be done.