What is the difference between the two fields? Why is the Assigned To field locked when my project is private however; the Assignee field is open to all users?
Assignee is the standard built-in field to designate the assignee for a task.
Assigned To is not any type of standard built-in field I’m aware of. It must be a custom field in your workspace that either a user created or perhaps it came from a template someone used?