SOAP API set project lead also sets default assignee

When setting the project lead (http://docs.atlassian.com/rpc-jira-plugin/latest/com/atlassian/jira/rpc/soap/beans/RemoteProject.html#setLead(java.lang.String)) using the soap API, the default assignee is also set (to project lead).

What's worse, the 'People' Admin UI shows the incorrect value.

To replicate:

1. Configure JIRA to allow unassigned issues
2. Set a TEST project, with a project lead but no default assignee.
3. Run the attached script (you might need to change user or project)
4. Note that in 'people', the default assignee is still unassigned.
5. Edit the people, and edit the default assignee. Notice that when editing, the default assignee is project lead.
6. Create an issue. Notice that the default assignee is the project lead.