[Koha] 22_to_30/move_marc_to_authheader.pl and MARC21 authorities

While upgrading Koha 2.2.8 to version 3.0.1, I encountered errors with move_marc_to_authheader.pl (migration_tools/22_to_30). That script fails to import authorities in MARC21 format. I found out that it is because it specifies UNIMARCAUTH in the $record->as_xml call, contrary to move_marc_to_biblioitems.pl which determines the MARC flavour before calling this function. I would like to know if it is still possible to use MARC21 for authorities in Koha 3 and in that case are the creation of 001, 152 and record leader in the script still necessary ? Regards Franck Magron