It’s so abstract I have to give examples. I’m really not interested in a debate about whether a spleen injury is fatal, and how quickly, so a classic game has a clock, called hit points. The messy business of exactly what it takes to kill a person (or a ‘tough’ person), which we would never all agree on (and/or don’t care to model) is replaced with a countdown. I may have been stabbed through the bicep, fictionally, but how dead does that make me? Well, 7 hit points closer to dead.

On the other hand, take a fight to the death between two squads. The fight is done when everyone’s dead, so if we’re resolving the action at a level that tells us when combatants are dead or not, then a clock to represent how my side is doing is unnecessary. It can either clash with the fiction (the other team is dead, but they win on points?), or it requires us to leave parts of the fiction vague (e.g. death MG Conflict) until the clocks finish.

Most games use clocks in predefined areas (hit points, DoW dispo); but since newer games encourage us to use them for ad hoc things, some care is in order.

I would totally use a clock to represent the morale of a unit, say, which is ephemeral (until the unit suddenly runs away), but clearly taking a 3-point hit to morale is bad if you only had 5.