I am on SuiteCRM 7.5.1
I see here in the SugarCRM developer guide this was some original functionality, and I see that this function allowed you to reassign all the records from one user to another.
This was so that, in our case, whenever we Terminate a User, I can easily reassign all the records to someone else rather than manually having to track down every sale, contact, lead, etc…
It doesn’t appear on the actions menu when you click on a User. I can see that if I change the url to say ‘&action=reassignUserRecords’, I pull up what appears to be the ability to change this, but the buttons to do so look like they lack some language file input.