The pst/sst010, pst/sst015, and pst/sst018 tables contain master data so are always archived and deleted. The pst/sst020, pst/sst025, and pst/sst028 tables are built using a sort key (pst/sst030) so are worthless when archived. Therefore, the standard sessions do not handle these tables. If you need to have active statistics in the archive company, you must rebuild them from the archived master data into compression (by sort key) tables.
Records in pst/sst020, pst/sst025, pst/sst028 resulting from archived master data tables are removed when "clear data for all companies" is set to "yes" in the "Update Sales Statistics" or "Update Purchase Statistics" sessions. The sort key (pst/sst030) tables are cleared as well.