thats perfectly normal.

Thats how all dbms works. Space is pre allocated to host user data most of the times, and when data is deleted from tables, the file is not automatically resized in the fs. This would be too costly to perform and would degrade performance os db. So most of them will prune space from disk in background and not so often.

Db2 for example does not even does that automatically. The DBa (me in this case) must have to perform the action to prune data files and revert space back to the filesystem