FileWave 13.2 has moved the execution of pre-/post-uninstallation scripts from delete to make inactive (called make passive in the code) fileset.
Before 13.2 pre-/post uninstallation scripts would run as part of the delete fileset action. Based on customer feedback, it was decided to change this in 13.2+ so that pre-/post uninstallation scripts will be run as part of the make fileset passive action. When a delete action is triggered, the client will check if the fileset is still active, in which case it will be made passive first, including running the pre-/post-uninstallation scripts (if there are any). More information here.