After some tests I discovered that when an asset is locked there is no versioning, even if the changes are made by the lock owner. Also, this lock only locks the metadata, the asset binary (or the actual image for example) is still open for anybody to edit it.
I reached out to Adobe on a support ticket and they said that there is no versioning on a locked asset by design.
Has anyone found a better solution? A solution that allows:
1) locking an asset (both binary and metadata)
2) allow the lock owner to modify the asset (both binary and metadata) and also version these changes.