> It's related to commits actually having a parent-child structure (forming a graph) and timestamps (commit/author) being metadata.

Yeah, I think everyone is aware. It's just that the last couple dozen commits, to me, looked like commits had been created in chronological order, so that topological order == chronological order.

> I know GitHub prefers sorting with author over commit date, but don't know how topology is handled.

Commits are usually sorted topologically.