I can see the pros, but more cons for deleting the test results when changes were made to the configuration of the run.
Currently, if you edit a test plan and alter the configuration of any of the runs, this will wipe out the test results for that run. I understand, or can guess as to why this is implemented this way, but with no warnings or "Are you sure?" confirmation, this has proved disastrous for me only one time (I learned my lesson permanently)! I have always wanted to write this up, and fear it is probably a duplicate.