I recently needed to add an employee list to some training but remembered that half the list was already in our system from a previous training. Rather than cross-reference the employee list and existing user list, I decided to use the CREATE action with Bulk User Management. I decided to do it this way because in the description of the action, it says, "This action is used to create a new user. If the user already exists, no action will be performed."
Turns out it created new users even if the user already existed, duplicating 40 users! This created a bit of a mess as some people logged in with their old credentials, some with the newly created ones, and I had to make sure whichever account they were using had the right access. I was quite frustrated as I only did this because the description said it wouldn't duplicate users.
Not sure if anyone else has experienced this or if I did something wrong, but I wanted to put it out there as an issue.