Ok, let me say this again ,since it looks that it wasn't read in the first time:
The events you have in a game are chosen in game gen after the map is laid according with a a RNG call and weighted by a pre-determined weight attached to the event definitions ( that is why eents have 2 weights: one is for the pick out in game gen and the other is the actual weight in game. More below ) . After the possible events in a game are chosen, the game will call every turn by the RNG to see if one ( or more ) of the chosen events is called ( that is where the 2nd weight is called ). This does not only depends on the weights every event has , but of the prereqs every event has ... that is probably why you'll see impeachement ( that requires a american civ ) far less than deer food

.And OFC there is the issue about having acess to all the options of the event ...
So we have 4 intervening layers:
- 1st RNG call during map creation to see what events will roll out . This is important since it happens after map creation and, because of that, games started via WB map/scenario ) will difer on this. Using your anedoctal data, you could easily have the same map saved from 4000 AD played by other persons and one could have no forest fires at all... not so fair now
- Prereqs check. You might have a game with a event active, but where, due to a fluke, you might never see it. Say, the example I gave above about the impeachement ( that event alone should had been enough to kill any conversation about event fairness

) or the Partisans event, that can never fire if you never raze a city of someone with emancipation ( if you don't enter in the areas where the event gets wonky due to bad coding ... ). OTOH you can easily have situations where a event that was suposed to rare becomes frequent due to uncommon abudance of prereqs ( the flight crash becomes annoyingly frequent if you have 10+ civs alive with flight and one of the options is free diplo

)
- 2nd RNG call every turn to see if a event is called. Pure random sheer luck ... nothing more to say. OFC that , depending of the 2 above, it can create some WTH situations, like strings of repeated events in the same spot ... forest fires, deer food, forge and theatre fires and slavery revolts are the more common offenders due to their high prereqs fullfillment odds.
- Events options possible. this is normally overlooked in the discussions, but even if the events averaged out in frequency and whatever, the avaliable options could still kill the show. The more frequent issue in here is the lack of money to buy out the bad options ( the

fire collection events ), but even the game options you are using can get things very wonky. The more extreme example is the spy caught event , that gives 2 EP related options and war with the offender.... all fine and dandy until you play with no espionage in 3.19, where the event has only one viable option
So, in the end, even if the events were well designed ( they aren't ) and if the weights were minimally fair ( they aren't ), the event code structure has so many quirks that you can't assure that events will cancel out, ever. It might happen to average in the metagame sense ( I do not beleive it ... my gut feeling is that the events are somewhat damaging in average in the long run ), but it will almost certainly
never happen in the course of one game. If that happens you lucked out ...