Chris Wanstrath, also known as @defunkt, highlights an improvement in GitHub's URL structure for tree browsing, moving from cumbersome, hash-heavy links to cleaner, more intuitive URLs. Previously, URLs included long hash strings that made navigation cumbersome, such as specific commits in the browsing path. The updated URLs simplify navigation by omitting these hashes and instead using clearer paths that enhance user experience by making it easier to reference specific branches and files. This change reflects a broader effort to streamline and improve the usability of GitHub's interface for developers.