BranchDeletedEvent is not fired when deleting a branch as part of a pull request merge

Summary

At the moment, deleting a branch as part of merging a pull request does not trigger the BranchDeletedEvent although https://docs.atlassian.com/bitbucket-server/javadoc/5.16.0/api/reference/com/atlassian/bitbucket/event/branch/BranchDeletedEvent.html states

An event that is raised when a branch is deleted using the UI or REST

Steps to Reproduce

1. Delete a branch explicitly (i.e. outside of merging a pull request) and observe the BranchDeletedEvent is fired
2. Merge a pull request and tick the box to delete the source branch, and observe the BranchDeletedEvent is not fired although the deletion happened through the UI and should therefore be fired according to the documentation