wsrep_sst_rsync has FreeBSD specific code in check_pid_and_port function to use sockstat instead of lsof.
However, there is still a wsrep_check_programs call looking for lsof in the main script, so if lsof is not in path the script still fails.
I removed the check, which allowed my cluster to sync successfully. Clearly not required on FreeBSD.
I presume this will be same in other versions besides 10.3