Optimistic locking discards all incoming changes that are relative to an older entity version. But everything has a cost and optimistic locking makes no difference.
The optimistic concurrency control mechanism takes an all-or-nothing approach even for non-overlapping changes. If two concurrent transactions are changing distinct entity property subsets then there’s no risk of losing updates.
Two concurrent updates, starting from the same entity version are always going to collide. It’s only the first update that’s going to succeed, the second one failing with an optimistic locking exception. This strict policy acts as if all changes are overlapping. For highly concurrent write scenarios, this single-version check strategy can lead to a large number of roll-backed updates.