We've used the terms diegetic and non-diegetic to describe narrative mechanics elsewhere in this guide, and in the core rules. The former means "mechanics that simulate what the character is actually doing in the fiction" and the latter means, "mechanics that simulate the narrative outcome the player wants."
When a player invokes a story tag like My Friend, the Fence, they're no longer interrogating the fiction. This would ordinarily be contrary to our goals in running the game, since we want players to always do things from within the fiction rather than from outside it.
But OSR+, despite being a simulationist game at heart, provides narrative mechanics to help players control the fiction. These mechanics, which include fate points and story tags, afford players a degree of fiat over outcomes ordinarily dictated by the dice.
Scarcity of Player Fiat
The gamist satisfaction that comes from playing (for players) lies in your ability to create a scarcity of player fiat in the game.
Understanding Player Incentives
As the GM, your fiat is virtually unlimited, but you're running the game with a different set of incentives than the players. The players want the narrative to go their way. What's more, because of narrative fulfillment (one of the qualities that make an RPG different than other games), that way the players want the narrative to go is also the way their PCs want their fictional lives to go. But we can't let things always go the players' way, otherwise there would be no challenge, and therefore no satisfaction.
The Role of the Dice
And so, enter the dice. The dice create opportunity for conflict and require you (and the players) to read them like tea leaves. The dice are swingy, and we like that swinginess because it's representative of how the real world works, being that it is fundamentally unpredictable.
The problem here is that we don't play RPGs to simulate the real world: we play to seek narrative fulfillment—or at least, that's the thesis of OSR+. Your players want their PCs to pull the sword out of the stone and fulfill their destiny; they want the wizardly maiden to rediscover the sorcery of her heritage and retake the kingdom; they want to defeat the necromancer who stole their soul and lay their burdens to rest. These are the fantasies the players wrote into session zero with the hope of fulfilling them through their PCs. And sometimes the random cruelty of the dice aren't enough to get them there.
That's why the narrative mechanics in OSR+ are important to the game, and important also in their scarcity. A little bit of control over the narrative creates opportunities for players to attempt to fulfill their imagined destinies. Whether they succeed, of course, is up to the dice.