In Dead Drop Falls, I saw a guy on Youtube find Exploding Bolts before he had even started Sorine's questchain. I also found them in exactly the same quantities and in the same place on my playthrough but I HAD done Sorine's quests so... This doesn't really make sense to me?

I thought the diffrence was when you did her quests this allowed you to make them...instead of relying on finding them.

Her quests send you to get schematics for the exploding bolts, allowing her and yourself to make them.

Definitely an oversight (or plain disinterest in correcting), but I wouldn't go as far as to call it a plot hole.

Depends... Do we know for sure no-one knew how to make them or did make them before the Dragonborn found them?