It seems that
is badly implemented since I didn't find any documentation concerning this change in moodle documentation.
Suddenly making this scope of a change should be better documented in Moodle documentation and also you should inform moodle administratos if this scope of a change is going to happen (one forum post doesn't really cut it).
To get it working again you now have to give coursecreator moodle/role:assign before they can get teacher role on the courses they create.
Also moodle/role:assign is concerned as a XSS-risk, risk of gaining other users information and users can spam other useers.