Completely empty but present blocks are cleared by an export / import. This is why the number of blocks can decrease even though all data is the same.
All unused Data blocks will be revoked and makes sure Essbase BSO apps do not have unused Cells for Data storage !!
The empty blocks is not considered fragmentation. It can be created through calc scripts, formulas & add to an existing database block count .
The only way to determine, if the Essbase database has an empty blocks exist then it will record the current block count, export the entire database, clear the database then import the exported data. If the block count decreased, the difference is the number of empty blocks that had existed in the database.
...or run CLEARBLOCK EMPTY.