I have created a custom post type "Events" and disabled "Comments" in Support-Section.
Then I have imported Event-posts via "WP All Import Pro" plugin from a CSV. This CSV did not any data that would have enabled the comments, but all newly generated Event-posts now have comment-capabilities when opening in frontend.
Weird: I cannot disable via "Quick Edit" and also not in Block-Editor-Mode.
When creating a new Event-post manually, comment-field is not displayed, only on those imported posts.