Somes users prefer to configure their .gitconfig name to be that of a username vs full name, so when the commit is stored it is that of the username. When a Stash Pull request is commited, it is stored on the git repo as the Last, Name (based on ldap pulled/populated information i assume).
So if a person would run reports on the on 'git log' results, it would show both usernames and "Last, Name" entries, which could be the same person. Basically the logic of the report would have to do lookups to match users.