the planner should automatically set when_to_transfer_output to ON_SUCCESS if the condor version on the submit node is 8.9.7 or higher

https://htcondor.readthedocs.io/en/latest/version-history/development-release-series-89.html?highlight=when_to_transfer_files

You may now specify that HTCondor only transfer files when the job succeeds (as defined by success_exit_code). Set when_to_transfer_files to ON_SUCCESS. When you do, HTCondor will transfer files only when the job exits (in the sense of ON_EXIT) with the specified success code. This is intended to prevent unsuccessful jobs from going on hold because they failed to produce the expected output (file(s)).