undocumented behaviour when Buildstream rebuilds all elements locally

I just tried doing a local build of a project, which has a cache server, the elements cached there are build with v1.1.1.

However my local version of Buildstream was v1.1.0, my local version contacted the cache and pulled certain elements, but then start rebuilding everything.

I updated to v1.1.1 and now it just pulls and uses the remote cached artifacts for my local build, nothing has been rebuilt.

Is this the expected behaviour, due to cache keys?

If so i can't see where this would be documented in the documentation.