As I’ve said, it doesn’t have to be a hostile or combat encounter. A social encounter is an encounter. An exploration challenge is an encounter. If the players follow the tracks and discover a basket of perfectly normal kittens, that’s an encounter. If the GM plans it out ahead of time, it’s an encounter. If they decide GM decides what made the tracks only when and if the PCs actually track it down, that’s still an encounter.
And no, this works with any game, not just AW. In BW, if the players decide to follow the tracks and, die rolls and GM permitting, find out who or what made them, then that’s an encounter. If they decide to ignore the tracks and continue onwards, they have bypassed it.
I think the 2024 DMG is much better written and while the text on creating adventures doesn't explicitly call out sandboxes but they do talk about giving the players meaningful options and choices and warns against railroads.
As relates to his specific post, here's how they now describe encounters:
Encounters are the individual scenes in the larger story of your adventure. Reduced to fundamentals, an encounter is an objective with an obstacle. It accomplishes one or more of the following:
- Moving characters closer to achieving a goal
- Frustrating the characters’ progress toward a goal
- Revealing new information