[Clipper]

Yes, the level loss happens only after you admit defeat in the combat and then resolve your attempt to Run Away from that monster.

Also note that monsters that don't pursue you do fight you. It is possible to kill these monsters if you have a high enough combat strength. What the non-pursuit clause means is that when you admit defeat in the combat, you can escape those monsters without rolling to Run Away from them. They will not chase you and cannot do their Bad Stuff to you.