Yeah, it makes sense to me for a couple of reasons. Flints aren't that cheap these days so getting as many shots as possible out of one seems like good economy. And, during a match or out hunting a slow fire or misfire translates into lost points or lost (or just wounded) game. Rather than fiddle with a balky flint during a match relay, better to have a ready spare to swap out if a quick knapping doesn't get it sparking good again. Shooting good scores is challenging enough without the disruption of your loading routine trying to troubleshoot a dumb piece of rock, or the mental distraction of wondering if it's going to go bang. Once back home, the partially worn flint can be rejuvenated by knapping, building its length back with JB Weld, trying bevel up vs. bevel down, grinding, whatever, and then used for practice where a slowfire could even be considered a good training exercise.
SCL