I just submitted a PR in one of my projects and was surprised to notice that the associated issue got automatically marked as resolved. I would expect this resolution to be triggered only when such PR gets merged, not just at time of submission.
Not sure you will be able to access the following given that it's a private repo (but feel free to access if you deem it necessary). The concrete case is: PR: https://bitbucket.org/mbari/tethysdash/pull-request/2 Issue: https://bitbucket.org/mbari/tethysdash/issue/25/
(Of course, we might be actually merging such PR, possibly before you take a look.)