It appears to me that Dependency CI is focused on dependency metadata, focusing on the state/version/license/etc the dependency declares.

Debian's CI focuses on actual run-time testing, specifically what it calls "as-installed" testing (as opposed to build-time testing). You don't test a specific build result, but whatever is installed in $PATH, $LD_LIBRARY_PATH, and so on.

Because the tested objects also use the as-installed dependencies -- libraries, modules, etc. -- whenever one of the dependencies changes, the dependents can automatically be re-tested for compatibility.