There are two issues here.
The first is to decide whether or not there should be an option to allow claiming of flagged posts to happen on a post level. Currently, if a staff member claims a review item for any of a topic’s posts, review items for any other posts in the topic are automatically assigned to them. Allowing review items to be claimed on the post level instead of the topic level is the change that was requested by @Loki.
The second issue is just something that I noticed while looking into this. As noted above, if multiple review items are generated for a topic and a staff member claims one of them, all review items for the topic will be automatically assigned to the staff member. As soon as the staff member acts on one review item (agrees, disagrees, etc) all of the topic’s review items that had previously been assigned to them will be automatically unassigned. This confused me when I saw it, but possibly it’s the intended behaviour.