I see nothing which could suggest that the planner would perform better under PostgreSQL 14.
But even if the database could optimize such OR-ed queries with indexes, I can not see how converting the query into UNION would degrade the performance. The database would style optimize the query by using the same indexes.

By the way here is a post explaining why using UNION is better for OR clause with joins: https://www.cybertec-postgresql.com/en/avoid-or-for-better-performance/.