Event Participant Exports Show wrong Results

I have created a Free Event with allowed multiple registration from same email address and added a profile to it with fields,
1) First Name
(Individual)
2 ) Last Name
(Individual)
3) Phone-Phone (Primary)
(Contact)
now when an anonymous participant registers himself along with one more participant with same email address , in db table civicrm_phone
two entries are done with same contact id and both marked as is_primary . Due to which when u export the participants list, the it shows wrong result. the issue is replicated on demo server @ : http://drupal.demo.civicrm.org/civicrm/event/info?reset=1&id=23

And Attached the csv exported for the event participants(actual 2 participant , but csv shows 4 participants) .