This is an expected behavior.

If Force FRBR is enabled on a pipe configuration, current  FRBR vectors (including the group ids) for records related to the pipe are deleted and new ones are created during the pipe. This results in new FRBR ids.

Clicking the "View X versions" button generates a search of all record group members in the index file, while the search request for data is performed on the DB. Until Indexing & Hotswapping (I&H) are complete, the "old" FRBR ids are used by the FE because they are still in the Primo Index. 
This could lead to discrepancy between the 2 - The index file, which has not yet been switched by the Hotswap, and the DB, which could be already updated by the update pipe.