The behavior is the same up through Jira 5.2 (v5.2#812-sha1:c4fbab6).
1. Set up one or more fields with more than one Context.
2. Have a Default Value for each Context.
3. Use "+Create Issue" button to bring up Create Form.
4. Check fields to ensure the proper Default Value for the given Context are set correctly.
5. Change the Project to one which also has a Default Value for the Field(s) in question.
6. Notice the value in the Field(s) is now set to None or are blank.