Slightly disturbing implication in #1003.

[Snails]

Certainly idea of XP for "story goals" and "adventure milestone rewards" has been commonly used since the ancient days of late 1e. I really have no idea whether that was an official or unofficial thing.

3e specifically talks about challenges broadly. The detailed rules are around combat, because D&D is build around a wargame chassis, and that serves the more common playstyles well enough, most of the time. The idea of non-combat challenges is definitely there.

4e does expand the concept of challenges into things that can be resolved by skill checks via explicit rules, where the skills available are up to the imagination of the players to make a good argument why such could apply if employed appropriately.