it seems LTI user syncronization doesn't unenrol users from the LTI provider course:
- Share course with LTI-registration method from the LTI Provider Moodle with settings:
User synchronisation: Yes
User synchronisation mode: enrol new and unenrol missing users.
- Enter LTI Provider Moodle course as a student from the LTI Customer site.
- Notice how student gets an student-role in LTI Provider site.
- Remove student from the LTI customer Moodle course.
- Notice that he/she isn't unenrolled from the LTI Provider Moodle even if you run "Publish as LTI tool users sync \enrol_lti\task\sync_members" by manually.