Lol, saying you are "beginning a process designed to delete your data" is a very different thing to actually deleting your data.
Cassandra is a database designed to make data as available as possible at the cost of possible inconsistency
When a data is deleted from Cassandra it's replaced by a marker named 'tombstone'
However backups, deep backups, and copies made on purpose for governments may exist
Law and advertisers mandate some data not being deletable