I ran the $ORACLE_HOME/rdbms/admin/sppurge for more than 95% of the data stored in the STATSPACK tables. The used space in the associated tablespace did not go down at all. STATSPACK is the only tool code using this tablespace.
How do I free up the space in the tablespace? It is LMT.
If you take a look into sppurge.sql script you can see that "delete" command used. Therefore hwm does't move and storage still allocated. If you really want to deallocate storage - use sptrunc.sql instead. But that will drop 100% statistics data.