What? Now we have quantum encounters? Sorry, ENCOUNTER is a game specific term. It requires certain things to happen and enough chance of failure that you can earn XP.
But it doesn't require anything else, other than risk.
No dice, no DM, no players, no table, nothing. And the term isn't quantum encounters, it's virtual encounters.
It's the same effect as the tree falling in the forest that nobody hears. It still fell. Some other trees nearby may have lost some branches when it fell.
Simply living through your life doesn't gain XP.
A very different issue; please see my post (1573) immediately above the one of yours I'm quoting for discussion on that.
Having encounters off-screen can and does gain xp for those who were there; it's the cumulative assumption of there having been many of these over time that allows the 9th-level NPC Fighter to walk into the room and ask to join the party.
Or do your PC's gain XP in downtime activities? After all, that would be fair, no? If NPC's continue to gain XP while not actually adventuring, then why don't your PC's? What's the rate?
Personally I think they should, but the rate of gain would be slow enough that unless they took half a year off most PCs might not even notice.
An encounter that isn't run ISN'T AN ENCOUNTER. It's narration by the DM.
And that narration is, in theory, based on said DM's best guess of the range of how the mechanics would have played out had they been played out, and then putting the narration somewhere within that range.
100 knights leave for the mountain pass and 17 return? If the DM looks at the situation and decides a reasonable range for how many would return from that trip is somewhere between 0 and 40 then sure, 17 works just fine. The mechanics and the narration suit each other, so what's the problem?
A much bigger issue would arise if it was later discovered that a reasonable return range would have been 65-95 out of 100 based on what's up there for them to meet. Now the DM's dug herself a hole in that her narration clashed with what the mechanics could be reasonably expected to produce.
Lan-"these poor knights"-efan