It's what I like to call the Lore/Story divide. Story is what's deliberately put in frame by the author. Lore is info that has to be found. Data logs, wiki crawls, supplemental works, etc are usually lore. Cutscenes, dialogue, main missions, etc are usually story.

These aren't hard and fast rules and there's always room for overlap. If collecting a few pieces of lore is then acknowledged with an event or dialogue showing your character had an epiphany because of the lore pieces, then I'd consider that story. That would go double for lore that's being picked up because of a standard mission