So are you saying that the functionality has changed? The former approach has worked until recently, and I find it strange that it works when logged in to wordpress and that the documentation (https://theeventscalendar.com/function/tribe_create_event/) does not reflect any changes.
Also it seems that the linked posts are handled in the saveEventMeta-function:
https://github.com/moderntribe/the-events-calendar/blob/4.3.2/src/Tribe/API.php#L122