I thought the implication was that it was a class ability or similar.I think it depends on the ability. Is it a magic item that does it and the PC knows it recharges at dawn? Then it's not a narrative mechanic, per se. But if it's a metacurrency-type ability that the PC doesn't really know about and it's up to the player to deploy, then I'd argue it's a narrative mechanic because the player is using it to pick the point in the narrative where the PC has an unbeatable skill check.