Please consult the Metadata Standards Working Group's Best Practice for Use of Field 914 wiki page for the latest updates.
UPDATE (June 2020):
As of June 9, 2020, LTS has instituted Alma Brief Level rules allowing Alma to automatically exclude records from publishing in OCLC if they lack certain elements (see Alma Brief Levels wiki page). However, if a record is exported from OCLC into Alma during the acquisitions process (i.e., awaiting full cataloging), the existence of OCLC number in the record trumps the criteria listed for exclusion and that particular record will push out to OCLC during the iterative Data Sync process. In that instance, you will still need to include 914 manually if the item is awaiting full cataloging. Once the item is fully cataloged, 914 should be removed from the bib record by the cataloger.
...