WebApi 'enrol_self_get_instance_info' password always 'Enrolment key'

Hello,

how can I query the self-enrolment password from a course with the WebApi?I tried the function "enrol_self_get_instance_info".

I only get "Enrollment key" as an answer.I never get the correct password as clear text.What am I doing wrong? Login as admin via webapi token.

Array
        (
            [id] => 370
            [courseid] => 97
            [type] => self
            [name] => Self enrolment (student)
            [status] => 1
            [enrolpassword] => Enrolment key
        )

Have a nice day.

Snowyrain